EP4649302A2

EP4649302A2 - Optoelectronic sensor system for monitoring a windshield of a vehicle

Info

Publication number: EP4649302A2
Application number: EP24700102.7A
Authority: EP
Inventors: Donald Peyrot; Vit Kadubec
Original assignee: Valeo Schalter und Sensoren GmbH
Current assignee: Valeo Schalter und Sensoren GmbH
Priority date: 2023-01-11
Filing date: 2024-01-09
Publication date: 2025-11-19
Also published as: WO2024149722A2; DE102023100514A1; WO2024149722A3; CN120457332A

Abstract

Disclosed herein is a vehicle sensor system (300) comprising an opto-electronic sensor (100). The opto-electronic sensor comprises a polarized light source (102) configured for illuminating a windshield (208) of a vehicle (302) within an illumination zone (206), wherein the illumination zone is above the opto-electronic sensor. The opto-electronic sensor further comprises a set of photo detector sensors (104) configured for providing sensor data (322) that is descriptive of scattered light (214) received from the illumination zone by the set of photo detector sensors. The opto-electronic sensor further comprises a set of linear polarizer filters (108, 110, 112, 114). Each filter is configured for filtering the scattered light before it reaches a respective one of the set of photo detectors. The set of linear polarizer filters comprise filters having a respective polarization axis rotated by between negative 2.5 degrees and 2.5 degrees (108), between 42.5 degrees and 47.5 degrees (110), between 87.5 degrees and 92.5 degrees (112), and between 132.5 degrees and 137.5 degrees (114) relative to a reference polarization axis (106).

Description

2022PF02455 - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Vehicle sensor system - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Description - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Field of the invention The invention relates to opto-electronic sensors, in particular to opto-electronic sensors configured for monitoring a windshield of a vehicle. Background and related art Vehicle windshields protect the driver and occupants during motion of the vehicle. However, they may become coated with condensation or water which may obscure the view of the driver as well as interfere with a heads-up display (HUD). Summary The invention provides for a vehicle sensor system, a vehicle, a method, and a computer program in the independent claims. Embodiments are given in the dependent claims. In one aspect the invention provides for a vehicle sensor system that comprises an opto- electronic sensor. The opto-electronic sensor comprises a polarized light source configured for illuminating a windshield of a vehicle within an illumination zone. The illumination zone is above the opto-electronic sensor. The opto-electronic sensor further comprises a set of photo detector sensors that is configured for providing sensor data that is descriptive of scattered light received from the illumination zone by the set of photo detector sensors. The opto-electronic sensor further comprises a set of linear polarizer filters. Each of the set of linear polarizer filters is configured for filtering the scattered light before it reaches a respective one of the set of photo detectors. The set of linear polarizer filters comprises filters having a respective polarization axis rotated nominally by 0°, 45°, 90°, and 135° relative to a reference polarization axis. The values of 0°, 45°, 90°, and 135° are the optional angular rotation of the various polarizing filters. In order to function these filters do not need to be at exactly this angular rotation. Changing the angle by + or – 2.5° would still allow the opto-electronic sensor to function properly. For example, the first linear polarizer filter may be positioned between -2.5° and +2.5° relative to the reference polarization axis. The second polarization filter may for example be between 42.5° and 47.5° relative to the reference polarization axis. The third linear polarization filter may for example be between 87.5° and 92.5° relative to the reference polarization axis. The fourth linear polarization filter may for example be between 132.5° and 137.5° relative to the reference polarization axis. The reference polarization axis as used herein is an arbitrarily rotated polarization axis that is nominally set to match the desired angular position of the first polarizing filter. This embodiment may have the benefit that it provides an integrated package for acquiring sensor data that is descriptive of scattered light that originates in the polarized light source. The polarized light source is positioned to illuminate the illumination zone and the set of photo detector sensors are configured to measure light scattered from the illumination zone. In another embodiment the vehicle sensor system further comprises a memory storing machine-executable instructions. The vehicle sensor system further comprises a computational system. Execution of the machine-executable instructions causes the computational system to receive the sensor data from the set of photo detector sensors. Execution of the machine-executable instructions further causes the computational system to calculate Stokes parameters descriptive of the scattered light using the sensor data. Execution of the machine-executable instructions further causes the computational system to optionally calculate a polarization state of light from the Stokes parameters. This embodiment may be beneficial because it may provide for an opto-electronic sensor which may be used to determine the presence of water either in liquid or solid form such as water, fog or ice on the windshield using the Stokes parameters. Execution of the machine-executable instructions further causes the computational system to calculate an angle of linear polarization from the Stokes parameters. Execution of the machine-executable instructions further causes the computational system to calculate a degree of linear polarization from the Stokes parameters. Execution of the machine- executable instructions further causes the computational system to determine a windshield status signal by comparing the polarization state of light (optionally), the angle of linear polarization, and the degree of linear polarization to a predetermined criterion. For example, the windshield status signal could be compared to a lookup table which has values and then assigns the windshield status signal using this lookup table. Execution of the machine-executable instructions further causes the computational system to provide the windshield status signal. The windshield status signal may for example be used to provide a signal to an operator of the vehicle. In other instances, the windshield status signal may be provided to an onboard computer system to modify the behavior of the vehicle, for example it may cause it to activate a defrosting action for the window or it may cause other things such as lowering the intensity of a heads-up display. In another embodiment the windshield status signal is a status indicating ice detected on the windshield. In another embodiment the windshield status signal is a status indicating a liquid detected on the windshield. This for example could be the detection of water. In another embodiment the windshield status signal is a status indicating a dry windshield for the windshield. This may be useful because it may be used for indicating that there is neither ice nor a liquid which is condensed on the windshield. In another embodiment if the windshield status is the status that either indicates that ice is detected on the windshield or a status indicating that liquid is detected on the windshield then the windshield status signal further comprises any one of the following: a brightness change command for the Heads up Display (HUD) of the windshield, a system deactivation command for the HUD of the windshield, an ice warning, a moisture warning, and windshield defrost commands. This embodiment may be beneficial because any of these commands may be used to automatically modify the behavior of the vehicle’s automatic systems in response to the detection of ice or liquid on the windshield in order to automatically remedy this view obstruction. In another embodiment the polarized light source is adapted for providing linearly polarized light for the illumination of the illumination zone. This may be beneficial because it may be useful for providing a clearer distinction between an icy windshield, a wet windshield, and a dry windshield. In another embodiment the polarized light source has a light source polarization axis. The light source polarization axis is rotated by 45° with respect to the reference polarization axis. This embodiment may be beneficial because it provides for polarized light source which can provide sensor data which can be clearly used to differentiate between a dry, wet, and icy windshield. In another embodiment the illumination zone is between 1 cm and 10 cm from the opto- electronic sensor. In another embodiment the illumination zone is between 2 cm and 7 cm from the opto- electronic sensor. This embodiment may be beneficial because it enables a sensor to be placed near or in the vicinity of the windshield but not directly against it. This for example may enable the placement of the opto-electronic sensor in the dashboard of a vehicle. Due to the close distance between the sensor and the windshield the risk of objects obstructing the sensors such as sunglasses or other objects sitting on the dashboard has a reduced chance of getting in between sensor and windshield. This reduced chance of obstruction may provide for more reliable results. In another embodiment the polarized light source comprises an infrared light source. The use of an infrared light source may be beneficial because this will be invisible to the operator of the vehicle and will not disturb or even blind the operator when the light source is active. In another embodiment the infrared light source is an infrared light emitting diode and a polarizing filter. This embodiment may be beneficial because it may provide an inexpensive means of providing the light source. In another embodiment the infrared light source is a solid-state infrared laser. This may be beneficial because it may be very compact and provide a means of illuminating a very small portion of the windshield. This might be relevant in case further IR-based tools are operated in the vehicle, like IR detectors for traffic detection, such as thermal imaging or infrared detectors. With the usage of a laser any potential negative effects e.g., resulting from scattered IR light may be minimized. Another aspect of the invention is a Head-Up-Display comprising the vehicle sensor system according to the description above. In another embodiment the vehicle sensor system further comprises the vehicle windshield. The vehicle windshield is positioned within the illumination zone. In another embodiment the polarized light source is configured such that it has an angle incidence with the windshield between 15° and 75°. In another embodiment of the vehicle sensor system, the vehicle sensor system further comprises a Head-Up-Display with a housing, wherein the Head-Up-Display comprises the opto-electronic sensor or parts thereof. The Head-Up-Display is configured to project an image into the windshield or onto a black panel on the windshield to provide information to the driver or other passengers of the vehicle. By having the opto-electronic sensor combined with the Head-Up-Display it is advantageously possible to check if the area of the windshield with the information for the driver is able to display the information correctly. Preferably, icing, dust and/or fogging of the information area can be detected with the vehicle sensor system and the Head-Up-Display can be operated more reliable. It is also possible that the Head-Up-Display comprises only the polarized light source or the set of photo detector sensors, which are parts of the opto-electronic sensor. In another embodiment of the vehicle sensor system at least the set of photo detector sensors is located inside or outside of the housing of the Head-Up-Display. That means that at least the set of photo detector sensors is arranged inside the Head-Up-Display such that the windshield or parts thereof, at least the area of the windshield with the information for the driver or other passengers, is visible for the set of photo detector sensors. Preferably, the set of photo detector sensors is arranged inside or outside of the optical path of the Head-Up-Display. Optical path of the Head-Up-Display means the path inside the housing of the Head-Up-Display that the light takes from the internal display of the Head-Up-Display to the windshield to project the information on the windscreen. Alternatively, the set of photo detectors is arranged outside of the housing of the Head-Up-Display, which means that the set of photo detectors is arranged on the outer surface of the housing or is a part of the housing. The same arrangement inside or outside the housing is also possible for the complete opto-electronic sensor or just the polarized light source. In another embodiment of the vehicle sensor system, the Head-Up-Display comprises a polarized light source, preferably the light source of an internal TFT display of the Head-Up- Display, whereby this light source is the polarized light source of the opto-electronic sensor. By having this feature the light source of the Head-Up-Display can advantageously be used additionally as the polarized light source for the sensor such that no additional light source is necessary. The set of photo detectors, arranged inside or outside the housing, detects the light from the Head-Up-Display which was reflected from the windshield such that the status of the windshield, for example clear, iced, dusty or fogged, can be assessed. In another embodiment of the vehicle sensor system the Head-Up-Display is configured to project an image onto the windshield, preferably onto a black panel on the windshield, whereby the opto-electronic sensor is located side-by-side with respect to the projection output of the Head-Up-Display. The projection output of the Head-Up-Display is the opening of the housing where the optical rays of the Head-Up-Display are emitted to project the image onto the windscreen. In this embodiment the opto-electronic sensor or parts thereof is arranged side-by-side to the opening in the housing. Preferably the opto- electronic sensor is arranged directly beside the opening or with a certain distance to the opening, preferably from 2 mm to 80 mm. Preferably, the opto-electronic sensor is arranged on the rim surrounding the housings opening, respectively the projection output. In another embodiment of the vehicle sensor system, the opto-electronic sensor is located side-by-side with respect to a display of the Head-Up-Display. This configuration is very useful for a so-called black panel Head-Up-Displays, which project the image directly from the display to a black panel on the windscreen. The display is installed in an opening of the dashboard to project the image to the windscreen. Due to the side-by-side arrangement of display and the sensor, the opto-electronic sensor is able to detect the status of the windscreen through the same opening of the dashboard. In another embodiment the vehicle windshield comprises a frit band. The frit band may also be referred to as the black print. The frit band is e.g., a black enamel band that is baked into the edges of the windshield. It is used for the purpose of adhering the windshield to the car. The opto-electronic sensor is positioned relative to the vehicle windshield such that illumination zone is within the frit band. This embodiment may be beneficial because the illumination takes place at a location where a potential restriction of the view by the operator of the vehicle due to technical components is irrelevant. The band forms an area that is inherently irrelevant to the driver's view, so that any components of the sensor system located there do not affect the operator. Further, since for example the frit band is transparent to infrared light, an infrared light source may be used to detect ice or condensation on the windshield through the frit band. In another embodiment the vehicle comprises a dashboard. The opto-electronic sensor is mounted at least partially within the dashboard. This embodiment may be beneficial because it provides a location for mounting the opto-electronic sensor. It Thus can be implemented in vehicles e.g., in a simple manner without the need to lay extra cables in a complicated manner to operate the sensor system. In the dashboard area, there are already a large number of cable harnesses, so that the wiring of the system could be simplified in this respect. In another aspect the invention provides for a vehicle comprising the windshield and the vehicle sensor system according to any one of the preceding claims. This embodiment may be beneficial because the vehicle will have a means of detecting if there is ice or condensation on the window. In another aspect the invention provides for a method of operating a vehicle sensor system. The vehicle sensor system comprises an opto-electronic sensor. The opto-electronic sensor comprises a polarized light source configured for illuminating a windshield of a vehicle within an illumination zone. The illumination zone is above the opto-electronic sensor. The opto-electronic sensor further comprises a set of photo detector sensors that are configured for providing sensor data that is descriptive of scattered light received from the illumination zone by the set of photo detector sensors. The opto-electronic sensor further comprises a set of linear polarizer filters, each filter being configured for filtering the scattered light before it reaches a respective one of the set of photo detectors. The first linear filter will have an orientation between -2.5° and 2.5° relative to the reference polarization axis. A second filter will have an orientation of between 42.5° and 47.5° relative to the reference polarization axis. A third filter will have an orientation between 87.5° and 92.5° relative to the reference polarization axis. A fourth filter will have an orientation between 132.5° and 137.5° relative to the reference polarization axis. The method comprises receiving the sensor data from the set of photo detector sensors. The method further comprises calculating Stokes parameters descriptive of the scattered light using the sensor data. The method further comprises optionally calculating a polarization state of light from the Stokes parameters. The method further comprises calculating an angle of the linear polarization from the Stokes parameters. The method further comprises calculating a degree of linear polarization from the Stokes parameters. The method further comprises determining a windshield status by comparing the polarization state of light (optionally), the angle of linear polarization, and a degree of linear polarization to a predetermined criterion. The method further comprises providing the windshield status signal. This could be provided either to an operator of the vehicle or it could also be provided to a computer or control system of the vehicle to perform an automatic action such as defrosting the window or reducing the brightness or intensity of a HUD. In another aspect the invention provides for a computer program comprising machine- executable instructions for execution by a computational system that is configured for controlling a vehicle sensor system. The computer program may, for example be stored on a non-transitory storage medium. The vehicle sensor system comprises an opto-electronic sensor. The opto-electronic sensor comprises a polarized light source that is configured for illuminating a windshield of a vehicle within an illumination zone. The illumination zone is above the opto-electronic sensor. The opto-electronic sensor further comprises a set of photo detector sensors that is configured for providing sensor data that is descriptive of scattered light that is received from the illumination zone by the set of photo detector sensors. The opto-electronic sensor further comprises a set of linear polarizer filters. Each filter is configured for filtering the scattered light before it reaches a respective one of the set of photo detectors. The first filter has an orientation of between -2.5° and 2.5° relative to the reference polarization axis. A second linear polarization filter has an orientation between 42.5° and 47.5° relative to the reference polarization axis. A third linear polarization filter has an orientation between 87.5° and 92.5° relative to the reference polarization axis. A fourth linear polarization filter has an orientation between 132.5° and 137.5° relative to the reference polarization axis. Execution of the machine-executable instructions causes the computational system to receive the sensor data from the set of photo detector sensors. Execution of the machine- executable instructions further causes the computational system to calculate Stokes parameters that are descriptive of the scattered light using the sensor data. Execution of the machine-executable instructions further causes the computational system to optionally calculate a polarization state of light from the Stokes parameters. Execution of the machine-executable instructions further causes the computational system to calculate an angle of linear polarization from the Stokes parameters. Execution of the machine- executable instructions further causes the computational system to calculate a degree of linear polarization from the Stokes parameters. Execution of the machine-executable instructions further causes the computational system to determine a windshield status signal by comparing the polarization state of light (optionally), an angle of linear polarization, and the degree of linear polarization to a predetermined criterion. Execution of the machine-executable instructions further causes the computational system to provide the windshield status signal. As will be appreciated by one skilled in the art, aspects of the present invention may be embodied as an apparatus, method or computer program product. Accordingly, aspects of the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a “circuit,” “module” or “system.” Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer readable medium(s) having computer executable code embodied thereon. Any combination of one or more computer readable medium(s) may be utilized. The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A ‘computer-readable storage medium’ as used herein encompasses any tangible storage medium which may store instructions which are executable by a processor or computational system of a computing device. The computer- readable storage medium may be referred to as a computer-readable non-transitory storage medium. The computer-readable storage medium may also be referred to as a tangible computer readable medium. In some embodiments, a computer-readable storage medium may also be able to store data which is able to be accessed by the computational system of the computing device. Examples of computer-readable storage media include, but are not limited to: a floppy disk, a magnetic hard disk drive, a solid state hard disk, flash memory, a USB thumb drive, Random Access Memory (RAM), Read Only Memory (ROM), an optical disk, a magneto-optical disk, and the register file of the computational system. Examples of optical disks include Compact Disks (CD) and Digital Versatile Disks (DVD), for example CD-ROM, CD-RW, CD-R, DVD-ROM, DVD-RW, or DVD-R disks. The term computer readable-storage medium also refers to various types of recording media capable of being accessed by the computer device via a network or communication link. For example, data may be retrieved over a modem, over the internet, or over a local area network. Computer executable code embodied on a computer readable medium may be transmitted using any appropriate medium, including but not limited to wireless, wire line, optical fiber cable, RF, etc., or any suitable combination of the foregoing. A computer readable signal medium may include a propagated data signal with computer executable code embodied therein, for example, in baseband or as part of a carrier wave. Such a propagated signal may take any of a variety of forms, including, but not limited to, electro-magnetic, optical, or any suitable combination thereof. A computer readable signal medium may be any computer readable medium that is not a computer readable storage medium and that can communicate, propagate, or transport a program for use by or in connection with an instruction execution system, apparatus, or device. ‘Computer memory’ or ‘memory’ is an example of a computer-readable storage medium. Computer memory is any memory which is directly accessible to a computational system. ‘Computer storage’ or ‘storage’ is a further example of a computer-readable storage medium. Computer storage is any non-volatile computer-readable storage medium. In some embodiments computer storage may also be computer memory or vice versa. A ‘computational system’ as used herein encompasses an electronic component which is able to execute a program or machine executable instruction or computer executable code. References to the computational system comprising the example of “a computational system” should be interpreted as possibly containing more than one computational system or processing core. The computational system may for instance be a multi-core processor. A computational system may also refer to a collection of computational systems within a single computer system or distributed amongst multiple computer systems. The term computational system should also be interpreted to possibly refer to a collection or network of computing devices each comprising a processor or computational systems. The machine executable code or instructions may be executed by multiple computational systems or processors that may be within the same computing device or which may even be distributed across multiple computing devices. Machine executable instructions or computer executable code may comprise instructions or a program which causes a processor or other computational system to perform an aspect of the present invention. Computer executable code for carrying out operations for aspects of the present invention may be written in any combination of one or more programming languages, including an object-oriented programming language such as Java, Smalltalk, C++ or the like and conventional procedural programming languages, such as the "C" programming language or similar programming languages and compiled into machine executable instructions. In some instances, the computer executable code may be in the form of a high-level language or in a pre-compiled form and be used in conjunction with an interpreter which generates the machine executable instructions on the fly. In other instances, the machine executable instructions or computer executable code may be in the form of programming for programmable logic gate arrays. The computer executable code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer or server. In the latter scenario, the remote computer may be connected to the user's computer through any type of network, including a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider). Aspects of the present invention are described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems) and computer program products according to embodiments of the invention. It is understood that each block or a portion of the blocks of the flowchart, illustrations, and/or block diagrams, can be implemented by computer program instructions in form of computer executable code when applicable. It is further under stood that, when not mutually exclusive, combinations of blocks in different flowcharts, illustrations, and/or block diagrams may be combined. These computer program instructions may be provided to a computational system of a general-purpose computer, special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the computational system of the computer or other programmable data processing apparatus, create means for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. These machine executable instructions or computer program instructions may also be stored in a computer readable medium that can direct a computer, other programmable data processing apparatus, or other devices to function in a particular manner, such that the instructions stored in the computer readable medium produce an article of manufacture including instructions which implement the function/act specified in the flowchart and/or block diagram block or blocks. The machine executable instructions or computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other devices to cause a series of operational steps to be performed on the computer, other programmable apparatus or other devices to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide processes for implementing the functions/acts specified in the flowchart and/or block diagram block or blocks. A ‘user interface’ as used herein is an interface which allows a user or operator to interact with a computer or computer system. A ‘user interface’ may also be referred to as a ‘human interface device.’ A user interface may provide information or data to the operator and/or receive information or data from the operator. A user interface may enable input from an operator to be received by the computer and may provide output to the user from the computer. In other words, the user interface may allow an operator to control or manipulate a computer and the interface may allow the computer to indicate the effects of the operator's control or manipulation. The display of data or information on a display or a graphical user interface is an example of providing information to an operator. The receiving of data through a keyboard, mouse, trackball, touchpad, pointing stick, graphics tablet, joystick, gamepad, webcam, headset, pedals, wired glove, remote control, and accelerometer are all examples of user interface components which enable the receiving of information or data from an operator. Brief description of the drawings In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which: Fig.1 shows a top view of an opto-electronic sensor; Fig.2 illustrates the opto-electronic sensor in operation; Fig.3 illustrates an example of a vehicle sensor system; and Fig.4 shows a flow chart which shows a method of operating the vehicle sensor system of Fig.3. Detailed Description Like numbered elements in these figures are either equivalent elements or perform the same function. Elements which have been discussed previously will not necessarily be discussed in later figures if the function is equivalent. Fig.1 shows a top view of an opto-electronic sensor 100 for a vehicle sensor system. The opto-electronic sensor 100 is shown as comprising a polarized light source 102 and a set of photo detector sensors. In this case there are four photo detector sensors. There is a reference polarization axis 106. There is a first linear polarizer filter 108 that is set at 0° with respect to the reference polarization axis 106. There is a second linear polarizer filter 110 set to 45° with respect to the reference polarization axis 106. There is a third linear polarizer filter 112 set at 90° relative to the reference polarization axis 106. There is a fourth linear polarizer filter 114 set at 135° with respect to the reference polarization axis 106. In one example the polarized light 102 has a polarization axis that is aligned with any one of the linear polarizer filters 108, 110, 112, 114. Underneath each of the linear polarizer filters 108, 110, 112, 114 there is a photo detector. These set of photo detector sensors 104 in conjunction with the linear polarizer filters 108, 110, 112, 114 enable the measurement of the Stokes parameters S0, S1, S2, and S3. From these first four parameters, one can calculate S4 and S5, which are related to the circular polarization. The signals measured by the photodiodes will provide values of intensity I at different polarization angles: I(x) (measured at 0° with respect to the reference polarization axis 106), I(+45°) (measured at 45° with respect to the reference polarization axis 106), I(y) (measured at 90° with respect to the reference polarization axis 106), and I(-45°) (measured at 135° with respect to the reference polarization axis 106). From this one can deduce the stokes parameters S₀, S₁, S₂ and S₃. Stokes’ formalism describes the polarization state of light (PSoL), e.g., for a wave propagating along the z axis, by using the following basic 4 parameters that are experimentally measured: S₀ = I(x) + I(y) S₁ = I(x) – I(y) S₂ = I(+45°) – I(-45°) S₃ = I(RHC) – I(LHC) where I(x), I(y), I(+45°), and I(-45°) are the intensities of light polarization components along, respectively, x, y, +45° and -45° directions as mentioned above; while I(RHC) and I(LHC) are the intensities of right handed circular (RHC) and left handed circular (LHC) polarization components of light. ^{It may be also shown that for partially polarized light} ^_^ ^{^} ≥ ^_^ ^{^} + ^_^ ^{^} + ^_^ ^{^} ^{while for a well polarized (coherent) light} ^_^ ^{^} = ^_^ ^{^} + ^_^ ^{^} + ^_^ ^{^} Thus, by measuring the first three components (S0, S1 and S2), one can also find the last component (S3) if light is polarized. Otherwise, the value of S3 may be only roughly estimated. From the Stokes parameters one can calculate other parameters. The Polarization state of light (PSoL) is: ^_^^^ The Angle of linear polarization AoLP is either of the following two equations: ^^^^ ^^^^ = arctan The Degree of linear polarization (DoLP) is: ^_^^^ Experimental measurements of AoLP and DoLP for a windshield (WS) are shown in the table below. AoLP DoLP WS 0.5863 0.5302 WS covered with 1.051 0.8130 paper WS covered with 1.388 0.9467 plastic WS covered with ice 0.6546 0.5796 WS covered with 0.8451 0.7016 thicker layer of ice In particular, the above results show that AoLP and DoLP may be used to identify the state of the windshield. Once AoLP and DoLP are known, they can be compared to prior measurements, such as in a look up table to determine the state of the windshield. Fig.2 illustrates the use of the opto-electronic sensor 100 with a clear windshield situation (illustration 200) and also with a windshield situation (illustration 202) in which ice is on the windshield 208. The depiction of ice on the outside of the windshield is illustrative. The ice or other moisture such as condensation may be on the inside of the window, the outside of the window, or on both the inside and outside of the window. Illustration 200 shows the opto-electronic sensor 100 directed towards a windshield 208. There is a distance 210 between the polarized light source 102 and the windshield 208. Above the polarized light source 102 is an illumination zone 206. The windshield 208 is within the illumination zone 206. The light 206 passes out of the polarized light source 102 and through the windshield 208. In this case it is a cone 204 of light. In illustration 200 only a minimal amount of light is scattered back to the set of photo detector sensors 104. Illustration 202 is very similar but there is now ice 212 on the outside of the windshield 208. There is now a substantial amount of scattered light 214 that goes back and is received by the set of photo detector sensors 104. In this case there is a cone of light 214 that is scattered back. Fig.3 illustrates a further example of a vehicle sensor system 300. It is shown as comprising a portion 302 of a vehicle. The vehicle comprises a dashboard 304 and a windshield 208. The opto-electronic sensor 100 is positioned on the dashboard 304 such that the polarized light source 102 directs a beam of infrared light 210 towards the windshield 208 at an angle of incidence 306. In this example there is ice 212 on the exterior of the windshield 208 causing the polarized light 210 to be scattered back as scattered light 214 towards the set of photo detector sensors 104. The placement of the ice on the exterior of the windshield in this figure is also illustrative. The ice or other condensation may alternatively be on the inside of the windshield, on the exterior of the windshield, or both on the inside and exterior of the windshield. Also shown is a so-called black band or frit band 308 that is part of the windshield 208. The frit band 308 is transparent to infrared light and does not e.g., interfere with the scattering of the light 210. In some examples, the opto-electronic sensor may be positioned such that the illumination zone is entirely within the frit band. The opto-electronic sensor 100 is shown as being exemplary connected to a control unit 310. The control unit 310 comprises a computational system 312 that is communication with a sensor interface 314. The sensor interface 314 is connected to the opto-electronic sensor. In some cases, the opto-electronic sensor may comprise some computational power and may send sensor data directly to the sensor interface 314. In other cases, the sensor interface 314 may do such things as providing power to the polarized light source 102 and bias the set of photo detector sensors 104 also. In this case the sensor interface 314 essentially measures the sensor data. The computational system 312 is further shown as optionally being in communication with a vehicle communication interface 316 that enables the computational system 312 to communicate and send messages to other computational or computers within the vehicle. The computational system 312 is shown as being in further communication with the memory 318. The memory 318 represents various types of memory that may be accessible to the computational system 312. In this example the computational system 312 is separate from other controllers or the main controller of the vehicle. In other examples the functionality of the control unit 310 may be integrated into the main computer or control system of the vehicle. The memory 318 is shown as containing machine-executable instructions 320. The machine-executable instructions 320 enable the computational system 312 to perform such tasks as performing numerical calculations and sending and receiving control signals. The memory 318 is further shown as containing sensor data 322 acquired from the opto- electronic sensor 100. This contains measurements from all four of the set of photo detector sensors 104. The memory 318 is shown as containing Stokes parameters 324 calculated from the sensor data 322. The memory 318 is further shown as optionally containing a polarization state of light 326 calculated from the Stokes parameters 324. The memory 318 is further shown as containing an angle of linear polarization 328 calculated from the Stokes parameters 324. The memory 318 is further shown as containing a degree of linear polarization 330 calculated from the Stokes parameters 324. The polarization state of light 326 (optionally), the angle of linear polarization 328 and the degree of linear polarization 330 may be analyzed in different ways. The memory 318 is shown as containing a first option which is a lookup table 332. The various values can be compared to the lookup table 332 to determine a windshield status signal 338. As an alternative to the lookup table 332 the memory 318 is also shown as containing a neural network 334. The neural network 334 could for example contain several fully connected layers and receive as input the polarization state of light 326 (optionally), the angle of linear polarization 328, and the degree of linear polarization 330. The output would then be the actual windshield status signal 338 that may for example indicate if the windshield is clean, has ice on it, has thick ice on it, or has condensation. The neural network 334 could be trained by acquiring data from when the windshield 208 is in different states and then using this as training data. As a further alternative the memory 318 is shown as containing a fuzzy logic module 336 which also takes these three inputs 326, 328, 330 and outputs the windshield status signal 338. Once the windshield status signal 338 has been determined it may be communicated via the communication interface 316 to other components or controllers within the vehicle. In some instances, the windshield status signal 338 may be used to control other things such as the brightness of the HUD, disabling of the HUD, or activating a defrost functionality of the vehicle 302. Fig.4 shows a flowchart which illustrates a method of operating the vehicle sensor 300. First, in step 400, the sensor data 322 is received from the set of photo detector sensors 104. Next, in step 402, the Stokes parameters 324 are calculated from the sensor data 322. Next, in step 404, the polarization state of light 326 is optionally calculated from the Stokes parameters 324. Then, in step 406, the angle of linear polarization 328 is calculated from the Stokes parameters 324. Next, in step 408, the degree of linear polarization 330 is calculated from the Stokes parameters 324. Next, in step 410, the windshield status signal 338 is determined by comparing the polarization state of light 326 (optionally), the angle of linear polarization 328, and the degree of linear polarization 330 to a predetermined criteria such as a lookup table 332 or the results from the neural network 334, or the fuzzy logic module 336. Finally, in step 412, the windshield status signal 338 is provided. For example, it may be communicated to other components of the vehicle using the vehicle communication interface 316. Fig.5 shows a further embodiment of the invention. The Head-Up-Display (500) has a housing (510) with a projection output (520). The Head-Up-Display (500) emits optical rays through the projection output (520) to project an image with information for the driver or any other passenger of a vehicle to a windscreen, which is not shown in this figure. In the housing (510) an optical path is provided from a display (not shown) to the opening with multiple mirrors (not shown) to provide an image with high quality. The opto-electronic sensor (100) is mounted on the rim surrounding the projection output (520) of the housing (510). Fig.6 shows a further embodiment of the invention for a black panel Head-Up-Display (500). The Head-Up-Display (500) is shown in a sectional view installed under a dashboard (not shown). The windscreen (208) in figure 6 is also shown sectional whereby the cutting plane of the sectional view is in the plane of the dashboard and below the surface of the dashboard. The Head-Up-Display has a housing (510) with a projection output (520), whereby the projection output here is established by a display, preferably a TFT display, which is mounted to the housing (510). The Head-Up-Display (500) emits optical rays through the projection output (520) to project an image with information for the driver or any other passenger of a vehicle to a windscreen (208). The opto-electronic sensor (100) is mounted side-by-side to the projection output (520) of the housing (510) respectively the display of the black panel Head-Up-Display (500).

List of Reference Numerals - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 100 opto-electronic sensor 102 polarized light source 104 set of photo detector sensors 106 reference polarization axis 108 first linear polarizer filter at 0° 110 second linear polarizer filter at 45° 112 third linear polarizer filter at 90° 114 fourth linear polarizer filter at 135° 200 light passes through windshield 202 light is scattered by ice on windshield 204 cone of light emitted by polarized light source 206 illumination zone 208 windshield 210 distance between polarized light source and windshield 212 ice on windshield 214 cone of scattered light 300 vehicle sensor system 302 portion of vehicle 304 dashboard 306 angle of incidence 308 frit band 310 control unit 312 computational system 314 sensor interface 316 vehicle communication interface 318 memory 320 machine executable instructions 322 sensor data 324 Stokes parameters 326 polarization state of light 328 angle of linear polarization 330 degree of linear polarization 332 look up table 334 neural network 336 fuzzy logic module 338 windshield status signal 400 receive the sensor data from the set of photo detector sensors 402 calculate Stokes parameters descriptive of the scattered light using the sensor data 404 optionally calculate a polarization state of light from the Stokes parameters 406 calculate an angle of linear polarization from the Stokes parameters 408 calculate a degree of linear polarization from the Stokes parameters 410 determine a windshield status signal by comparing the polarization state of light (optionally), the angle of linear polarization, and the degree of linear polarization to a predetermined criteria 420 provide the windshield status signal 500 Head-Up-Display 510 Housing of the Head-Up-Display 520 Projection output of the Head-Up-Display

Claims

Claims - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - Claim 1. A vehicle sensor system (300) comprising an opto-electronic sensor (100), wherein the opto-electronic sensor comprises: - a polarized light source (102) configured for illuminating a windshield (208) of a vehicle (302) within an illumination zone (206), wherein the illumination zone is above the opto-electronic sensor; - a set of photo detector sensors (104) configured for providing sensor data (322) that is descriptive of scattered light (214) received from the illumination zone by the set of photo detector sensors; - a set of linear polarizer filters (108, 110, 112, 114), each filter being configured for filtering the scattered light before it reaches a respective one of the set of photo detectors, wherein the set of linear polarizer filters comprise filters having a respective polarization axis rotated by between negative 2.5 degrees and 2.5 degrees (108), between 42.5 degrees and 47.5 degrees (110), between 87.5 degrees and 92.5 degrees (112), and between 132.5 degrees and 137.5 degrees (114) relative to a reference polarization axis (106). Claim 2. The vehicle sensor system of claim 1, wherein the vehicle sensor system further comprises: - a memory (318) storing machine executable instructions (320); - a computational system (312), wherein execution of the machine executable instructions causes the computational system to: - receive (400) the sensor data from the set of photo detector sensors; - calculate (402) Stokes parameters (324) descriptive of the scattered light using the sensor data; - preferably calculate (404) a polarization state of light (326) from the Stokes parameters; - calculate (406) an angle of linear polarization (328) from the Stokes parameters; - calculate (408) a degree of linear polarization (330) from the Stokes parameters; - determine (410) a windshield status signal (338) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criteria, wherein the polarization state of light is preferably compared to the predetermined criteria also during determination of the windshield status signal; and - provide (420) the windshield status signal. Claim 3. The vehicle sensor system of claim 2, wherein the windshield status signal is any one of the following: - a status indicating ice detected on the windshield; - a status indicating a liquid detected on the windshield; and - a status indicating a dry windshield for the windshield. Claim 4. The vehicle sensor system of claim 3, wherein if the windshield status is the status indicating ice detected on the windshield or a status indicating the liquid detected on the windshield then the windshield status signal further comprises any one of the following: a brightness change command for a HUD of the windshield, a system deactivation command for the HUD of the windshield, an ice warning, a moisture warning, and windshield defrost commands. Claim 5. The vehicle sensor system of any one of the preceding claims, wherein the polarized light source is adapted for providing linearly polarized light for the illumination of the illumination zone. Claim 6. The vehicle sensor system of any one of the preceding claims, wherein the illumination zone is between 1 cm and 10 cm from the opto-electric sensor, and wherein the illumination zone is preferably between 2 cm and 7 cm from the opto-electric sensor. Claim 7. The vehicle sensor system of any one of the preceding claims, wherein the polarized light source comprises an infrared light source. Claim 8. The vehicle sensor system of any one of the preceding claims, wherein the infrared light source is anyone of the following: - an infrared light emitting diode and a polarizing filter, and - a solid state infrared laser. Claim 9. The vehicle sensor system of any one of the preceding claims, wherein the vehicle sensor system further comprises the vehicle windshield, wherein the vehicle windshield is positioned within the illumination zone. Claim 10. The vehicle sensor system of claim 9, wherein the polarized light source is configured such that it has an angle of incidence (306) with the windshield between 15 degrees and 75 degrees. Claim 11. The vehicle sensor system of claim 9 or 10, wherein the vehicle sensor system further comprises a Head-Up-Display (500) with a housing (510), wherein the Head- Up-Display (500) comprises the opto-electronic sensor (100) or parts thereof. Claim 12. The vehicle sensor system of claim 11, wherein at least the set of photo detector sensors (104) are located inside or outside of the housing (510) of the Head-Up- Display (500). Claim 13. The vehicle sensor system of claim 11 or 12, wherein the Head-Up-Display (500) comprises a polarized light source, preferably the light source of an internal TFT display of the Head-Up-Display (500), whereby this light source is the polarized light source (102) of the opto-electronic sensor (100). Claim 14. The vehicle sensor system of one of the claims 11 to 13, wherein the Head- Up-Display (500) is configured to project an image onto the windshield (208), preferably onto a black panel on the windshield (208), whereby the opto-electronic sensor (100) is located side-by-side with respect to the projection output (520) of the Head-Up-Display (500). Claim 15. The vehicle sensor system of claim 9 or 10, wherein the vehicle windshield comprises a frit band (308), wherein the opto-electronic sensor is positioned such that the illumination zone is within the frit band. Claim 16. The vehicle sensor system of one of the claims 9, 10 or 11, wherein the vehicle comprises a dashboard (304), wherein the opto-electronic sensor is mounted at least partially within the dashboard. Claim 17. A vehicle (302) comprising the windshield and the vehicle sensor system according to any one of the preceding claims. Claim 18. A method of operating a vehicle sensor system (300) comprising an opto- electronic sensor (100), wherein the opto-electronic sensor comprises: - a polarized light source (102) configured for illuminating a windshield (208) of a vehicle (302) within an illumination zone (206), wherein the illumination zone is above the opto-electronic sensor; - a set of photo detector sensors (104) configured for providing sensor data (322) that is descriptive of scattered light (214) received from the illumination zone by the set of photo detector sensors; - a set of linear polarizer filters (108, 110, 112, 114), each filter being configured for filtering the scattered light before it reaches a respective one of the set of photo detectors, between negative 2.5 degrees and 2.5 degrees (108), between 42.5 degrees and 47.5 degrees (110), between 87.5 degrees and 92.5 degrees (112), and between 132.5 degrees and 137.5 degrees (114) relative to a reference polarization axis (106); wherein the method comprises: - receiving (400) the sensor data from the set of photo detector sensors; - calculating (402) Stokes parameters (324) descriptive of the scattered light using the sensor data; - preferably calculating (404) a polarization state of light (326) from the Stokes parameters; - calculating (406) an angle of linear polarization (328) from the Stokes parameters; - calculating (408) a degree of linear polarization (330) from the Stokes parameters; - determining (410) a windshield status signal (338) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criteria, wherein the polarization state of light is preferably compared to the predetermined criteria also during determination of the windshield status signal; and - providing (420) the windshield status signal. Claim 19. A computer program comprising machine executable instructions (320) for execution by a computational system (312) configured for controlling a vehicle sensor system (300), wherein the vehicle sensor system comprises an opto-electronic sensor (100), wherein the opto-electronic sensor comprises: - a polarized light source (102) configured for illuminating a windshield (208) of a vehicle (302) within an illumination zone (206), wherein the illumination zone is above the opto-electronic sensor; - a set of photo detector sensors (104) configured for providing sensor data (322) that is descriptive of scattered light (214) received from the illumination zone by the set of photo detector sensors; and - a set of linear polarizer filters (108, 110, 112, 114), each filter being configured for filtering the scattered light before it reaches a respective one of the set of photo detectors, wherein the set of linear polarizer filters comprise filters having a respective polarization axis rotated by between negative 2.5 degrees and 2,5 degrees (108), between 42.5 degrees and 47.5 degrees (110), between 87.5 degrees and 92.5 degrees (112), and between 132.5 degrees and 137.5 degrees (114) relative to a reference polarization axis (106); wherein execution of the machine executable instructions causes the computational system to: - receive (400) the sensor data from the set of photo detector sensors; - calculate (402) Stokes parameters (324) descriptive of the scattered light using the sensor data; - preferably calculate (404) a polarization state of light (326) from the Stokes parameters; - calculate (406) an angle of linear polarization (328) from the Stokes parameters; - calculate (408) a degree of linear polarization (330) from the Stokes parameters; - determine (410) a windshield status signal (338) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criteria, wherein the polarization state of light is preferably compared to the predetermined criteria also during determination of the windshield status signal; and - provide (412) the windshield status signal. Claim 20. A Head-Up-Display (500) comprising the vehicle sensor system according to any one of the claims 1 to 8.