Monitoring of driving surfaces

Abstract

Disclosed herein is a vehicle sensor system (600) comprising an opto-electronic sensor (100). The execution of machine executable instructions (612) causes a computational system (604) to: receive (702) sensor data (614) from a set of photo detector sensors (104); calculate (704) Stokes parameters (616) descriptive of the scattered light using the sensor data; calculate (706) an angle of linear polarization (620) from the Stokes parameters; calculate (708) a degree of linear polarization (622) from the Stokes parameters; determine (710) a driving surface status signal (632) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion; and provide (712) the driving surface status signal.

Description

[0001] Monitoring of Driving Surfaces

[0002] Description

[0003] Field of the invention

[0004] The invention relates to opto-electronic sensors, in particular to opto-electronic sensors configured for monitoring a driving surface.

[0005] Background and related art

[0006] Driving surfaces such as roads or parking lots may have different surface conditions such as being dry, icy, or wet. It may not necessarily be apparent to a driver in what condition the driving surface is.

[0007] Summary

[0008] 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.

[0009] The invention provides for a vehicle sensor system, a vehicle, a method of operating a vehicle sensor system, and a computer program in the independent claims. Embodiments are given in the dependent claims.

[0010] In one aspect the invention provides for a vehicle sensor system comprising an optoelectronic sensor. The opto-electronic sensor comprises a light source configured for illuminating an illumination zone on a driving surface adjacent to a vehicle. The light source is configured to generate near infrared linearly polarized light. The opto-electronic sensor further comprises a set of photo detector sensors 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 is configured for filtering the scattered light before it reaches a specific one of the set of photo detectors. The set of linear polarized filters comprise filters having a respective polarization axis rotated between -2.5 degrees and 2.5 degrees, between 42.5 degrees and 47.5 degrees, between 87.5 degrees and 92.5 degrees, and between 132.5 degrees and 137.5 degrees relative to a reference polarization axis.

[0011] 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 machineexecutable 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 calculate an angle of linear polarization from the Stokes parameters. Execution of the machineexecutable 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 driving surface status signal by comparing the angle of linear polarization and the degree of linear polarization to a predefined criterion. Execution of the machine-executable instructions further causes the computational system to provide the driving surface status signal.

[0012] In another aspect the invention provides for a vehicle comprising the vehicle sensor system according to an embodiment.

[0013] In another aspect the invention provides for a method of operating a vehicle sensor system comprising an opto-electronic sensor according to an embodiment. The method comprises controlling illumination of the illumination zone on the driving surface adjacent to the vehicle using the light source. The method further 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 calculating an angle of 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 driving surface status signal by comparing the angle of linear polarization and the degree of linear polarization to a predefined criterion. The method further comprises providing the driving surface status signal.

[0014] In another aspect the invention provides for a computer program comprising machineexecutable instructions configured for controlling a computational system to perform an embodiment of the method.

[0015] Brief description of the drawings

[0016] In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

[0017] Fig. 1 shows a top view of an opto-electronic sensor;

[0018] Fig. 2 shows a side view of an opto-electronic sensor;

[0019] Fig. 3 illustrates the use of a vehicle sensor system;

[0020] Fig. 4 illustrates the further use of the vehicle sensor system;

[0021] Fig. 5 illustrates a further use of a vehicle sensor system;

[0022] Fig. 6 illustrates the illustrates a vehicle sensor system; and

[0023] Fig. 7 shows a flow chart which illustrates the use of the vehicle sensor system of Fig. 6.

[0024] Detailed Description

[0025] 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.

[0026] In an example, a vehicle sensor system comprises an opto-electronic sensor. The optoelectronic sensor comprises a light source configured for illuminating an illumination zone on a driving surface adjacent to a vehicle. Driving surfaces may include, but are not limited to: roads, paved surfaces, and parking lots. The light source is configured to generate near infrared linearly polarized light. The opto-electronic sensor further comprises a set of photo detector sensors configured for providing sensor data that is descriptive of scattered light received from the illumination zone by the set of photo detector sensors. In some examples the light source and the set of photo detector sensors are combined in the single package. In other examples they are mounted, for example, on the vehicle separately.

[0027] The opto-electronic sensor comprises a set of linear polarizer filters. Each filter being configured for filtering the scattered light before it reaches a specific one of the set of photo detectors. The set of linear polarizer filters comprises filters having a respective polarization axis rotated by between -2.5 degrees and 2.5 degrees, between 42.5 degrees and 47.5 degrees, between 87.5 degrees and 92.5 degrees, and between 132.5 degrees and 137.5 degrees relative to a reference polarization axis.

[0028] 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 machineexecutable 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 calculate an angle of linear polarization from the Stokes parameters. Execution of the machineexecutable instructions further causes the computational system to calculate a degree of linear polarization from the Stokes parameters.

[0029] Execution of the machine-executable instructions further causes the computational system to determine a driving surface status signal by comparing the angle of the linear polarization and the degree of linear polarization to a predefined criterion. For example, the angle of linear polarization and degree of linear polarization could be compared to values taken from a lookup table which is used to then determine from the range of these values the driving surface status signal. Execution of the machine-executable instructions further causes the computational system to provide the driving surface status signal. This example may be beneficial because it may provide for a means of identifying the status or the state of a driving surface such as it being wet or covered with ice automatically. The light source is an infrared linearly polarized light. As it is infrared it may be shone, for example, in front of a vehicle without the fear of blinding other drivers. As the infrared linearly polarized light hits the illumination zone the scattered light will have a distinctive value for the angle of linear polarization and degree of linear polarization depending upon the status of the driving surface.

[0030] In another example the driving surface status signal is any one of the following: a status indicating ice detected on the driving surface, a status indicating water detected on the driving surface, and a status indicating dry surface detected on the driving surface. This example may be beneficial because it may provide not only a means of warning or informing an operator of the vehicle but it may also be used to change the behavior and function of systems of a vehicle. For example, it may be used to update or change the behavior of an automated driving system. In other examples, it may also cause a vehicle to go into a state when there is ice or water detected to automatically increase the distance between vehicles.

[0031] In another example if the driving surface status signal indicates water or ice on the driving surface an execution of the machine-executable instructions further causes the computational system to perform any one of the following: issue a vehicle speed reduction command, issue an increased minimum distance to a next vehicle command, issue an icy road warning using a user interface if the driving surface status indicates ice on the driving surface, and issue a wet road warning using the user interface if the driving surface status signal indicates water on the driving surface. This example may be beneficial because it may for example provide for a means of automatically configuring vehicle systems within a vehicle as well as providing information which may assist an operator in driving the vehicle more safely. In another example, the vehicle sensor system is configured to be mounted on a front surface of the vehicle. The illumination zone is in front of the vehicle. This embodiment may be beneficial because it may provide for a warning of ice or water that is in front of the vehicle where the vehicle is driving.

[0032] In another example the vehicle sensor system is configured to be mounted on an underside of the vehicle facing the driving surface. For example, the vehicle sensor system could be mounted in front of a wheel. This embodiment may be beneficial because it may require a smaller illumination zone than choosing it in front of the vehicle. For example, this may enable the sensor to be closer to the driving surface which means that a larger portion of the light shone on the driving surface will be scattered back into the set of photo detector sensors. This may in some instances provide for a more accurate detection or determination of the driving surface status signal. It may also provide for a reduced cost because the need for a large or bright light source may be reduced.

[0033] In another example the light source is any one of the following: a light emitting diode, a laser diode, and an illumination system of a LIDAR system. The use of the LIDAR system may be particularly beneficial because it may already be present in a vehicle. In this case, the vehicle sensor system could be constructed by simply adding an additional set of photo detector sensors and polarizing filters.

[0034] In another example, execution of the machine-executable instructions further causes the computational system to calculate a polarization state of light from the Stokes parameters. Execution of the machine-executable instructions further causes the computational system to compare the polarization state of the light to the predetermined criteria also during determination of the driving surface status signal. This for example may be beneficial because also determining the polarization state of light and using it may further provide for a means of more accurately determining the driving surface status. In another example, the opto-electronic sensor further comprises a set of lenses. Each lens is configured for focusing the scattered light onto a specific one of the set of photo detectors. In this example, each of the photo detectors has an individual lens which is used to help collect light and then focus it on a particular photo detector. This may be beneficial because it may provide for increased accuracy in determining the driving surface status signal. The use of individual lenses may also have the benefit of for example using a single lens or set of camera lenses which are used collectively on the individual photo detector sensors. Individual lenses may be used to gather light from a larger solid angle and concentrate them on individual photo detector sensors.

[0035] In another example, a vehicle comprises the vehicle sensor system according to an example. This may be beneficial because then the vehicle may be configured to automatically detect the road conditions as indicated by the driving surface status signal. This may provide for better automation of the vehicle as well as for safer driving of the vehicle due to the operator being better aware of road conditions.

[0036] 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. The polarized light source may be configured to generate near infrared polarized light. In this example 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 SO, SI, S2, and S3. From these first four parameters, one can calculate S4 and S5, which are related to the circular polarization.

[0037] The signals measured by the photodiodes will provide values of intensity I at different polarization angles: l(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).

[0038] From this one can deduce the stokes parameters So, Si, 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:

[0039] So= l(x) + l(y)

[0040] 51 = l(x) - l(y)

[0041] 52= I (+45°) - 1 (-45°)

[0042] 53= l(RHC) - l(LHC) where l(x), l(y), l(+45°), and l(-45°) are the intensities of light polarization components along, respectively, x, y, +45° and -45° directions as mentioned above; while l(RHC) and l(LHC) are the intensities of right handed circular (RHC) and left handed circular (LHC) polarization components of light.

[0043] It may be also shown that for partially polarized light

[0044] S02> S + S + S32while for a well polarized (coherent) light

[0045] S$ = Sf + S' + s32 Thus, by measuring the first three components (So, Si and S2), one can also find the last component (S3) if light is polarized. Otherwise, the value of S3 may be only roughly estimated.

[0046] From the Stokes parameters one can calculate other parameters. The Polarization state of light (PSoL) is:

[0047] PSoL

[0048] The Angle of linear polarization AoLP is either of the following two equations:

[0049] AoLP

[0050] AoLP = arctan

[0051] The Degree of linear polarization (DoLP) is:

[0052] DoLP

[0053] Fig. 2 shows a side view of the opto-electronic sensor 100. In this example the polarized light source 102 is formed by an LED 200 which emits infrared light. This light is then focused by the lens 202 which then goes through a polarizer filter 204 to produce linearly polarized infrared light 206. This linearly polarized infrared light is then directed at the illumination zone on a driving surface that is adjacent to the vehicle. Some of this light is then scattered and is the scattered light 208. This then passes through an optional lens 210 to cause the scattered light to become concentrated 208'. This light then goes through a linear polarizer filter 112 where it is then measured by the photo detector 104. The example illustrated in Figs. 1 and 2 may be modified in several examples. For example, the polarized light source 102 could be located at a different position or component than the set of photo detector sensors 104. The lenses 202 and 210 may or may not be present depending upon the example. In some examples, the LED 200 may be replaced with an infrared laser, in which case the polarizer filter 204 and the lens 202 may not be necessary.

[0054] Fig. 3 illustrates a vehicle 300 on a driving surface 302. The driving surface 302 may for example be a road or other surface which the vehicle 300 can drive on. The opto-electronic sensor 100 is shown as being mounted in a forward position on the windshield of the vehicle 300. The linearly polarized infrared light 206 is shown as being directed towards an illumination zone 304 on the surface of the driving surface 302. Light would then be scattered from this illumination zone 304 back to the opto-electronic sensor 100 to be measured by the set of photo detector sensors 104.

[0055] Fig. 4 shows a view from inside of the vehicle 300. The dashed line marked 304 indicates the location of the illumination zone 304 on the driving surface 302.

[0056] Fig. 5 shows an alternate position for the opto-electronic sensor 100. In this example, the opto-electronic sensor 100 is mounted on an underside 500 of the vehicle 300. It is positioned directly in front of a wheel 502. The opto-electronic sensor 100 is mounted closer to the driving surface 302. A smaller amount of linearly polarized infrared light 206 is needed to acquire the scattered light 208.

[0057] Fig. 6 illustrates an example of a vehicle sensor system 600. The vehicle sensor system 600 could for example be integrated into the examples illustrated in Figs. 3, 4, or 5. In this example, the opto-electronic sensor 100 is shown as shining linearly polarized infrared light 206 in the illumination zone 304 on the driving surface 302. The scattered light 208 is reflected back towards the set of photo detector sensors 104. The opto-electronic sensor 100 is then shown as being connected to a sensor interface 606 of a control unit 602.

[0058] The control unit 602 is shown as having a computational system 604 that is in communication with the sensor interface 606, a memory 610 and optionally a vehicle communication interface 608. The memory 610 is intended to represent various types of memory which may be accessible to the computational system 604. The vehicle communication interface 608 may enable the computational system 604 to send various messages and commands and receive data from other components of the vehicle 300.

[0059] The memory 610 is shown as containing machine-executable instructions 612. The machine-executable instructions 612 enable the computational system 604 to perform various numerical and control tasks. The memory 610 is further show as containing sensor data 614 that has been received from the opto-electronic sensor 100. The memory 610 is further shown as containing Stokes parameters 616 that have been calculated from the sensor data 614. The memory 610 is further shown as optionally containing the polarization state of light 618 that has been calculated from the Stokes parameters 616. The polarization state of light 618 may be optionally used when determining the driving surface status signal 632. The memory 610 is further shown as containing the angle of linear polarization calculated from the Stokes parameters 616.

[0060] The memory 610 if further shown as containing the degree of linear polarization calculated from the Stokes parameters 616. The memory 610 if further shown as containing a predefined criterion 624 against which the angle of linear polarization 620, the degree of linear polarization 622, and optionally the polarization state of light 618 to determine the driving surface status signal 632. The memory is further shown as containing the driving surface status signal 632 that was determined by comparing at least the angle of linear polarization 620 and the degree of linear polarization 622 against the predefined criterion 624. The predefined criterion 624 may be supplied in a variety of ways. The memory 610 is further shown as containing a lookup table 626 which may be used to provide the predefined criterion 624. In other examples, a neural network 628 or a fuzzy logic module 630 may also be used.

[0061] The neural network 628 could for example contain several fully connected layers and receive as input the polarization state of light (optionally), the angle of linear polarization 620, and the degree of linear polarization 622. The output may then be the actual driving surface status signal 632 that may for example indicate if the driving surface is clean, has ice on it, or has water on the surface. The neural network 628 could be trained by acquiring data from when the driving surface 302 is in different states and then using this as training data.

[0062] As a further a fuzzy logic module 630 which also takes as input the polarization state of light (optionally), the angle of linear polarization 620, and the degree of linear polarization 622. and outputs the driving surface status signal 632.

[0063] Fig. 7 shows a flowchart which illustrates a method of operating the vehicle sensor system 600 of Fig. 6. In step 700, the illumination zone 304 is illuminated on the driving surface 302 using the light source 102. In step 702, the sensor data 614 is received from the set of photo detector sensors 104. In step 704, the Stokes parameters 616 are calculated using the sensor data 614. In step 706, the angle of linear polarization 620 is calculated from the Stokes parameters 616. In step 708, the degree of linear polarization 622 is calculated from the Stokes parameters 616. In step 710, the driving surface status signal 632 is determined by comparing the angle of linear polarization 620 and the degree of linear polarization 622 to the predefined criterion 624. In step 712, the driving surface status signal 632 is provided.

[0064] 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.

[0065] 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.

[0066] '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.

[0067] 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.

[0068] 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.

[0069] 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).

[0070] 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.

[0071] 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.

[0072] 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.

[0073] 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.

[0074] List of Reference Numerals

[0075] 100 opto-electronic sensor

[0076] 102 polarized light source

[0077] 104 set of photo detector sensors

[0078] 106 reference polarization axis

[0079] 108 first linear polarizer filter at 0°

[0080] 110 second linear polarizer filter at 45°

[0081] 112 third linear polarizer filter at 90°

[0082] 114 fourth linear polarizer filter at 135°

[0083] 200 LED

[0084] 202 lens

[0085] 204 polarizer filter

[0086] 206 linearly polarized infrared light

[0087] 208 scattered light

[0088] 208' concentrated scattered light

[0089] 210 lens

[0090] 300 vehicle

[0091] 302 driving surface

[0092] 304 illumination zone

[0093] 500 underside of vehicle

[0094] 502 wheel

[0095] 600 vehicle sensor system

[0096] 602 control unit

[0097] 604 computational system

[0098] 606 sensor interface

[0099] 608 vehicle communication interface

[0100] 610 memory

[0101] 612 machine executable instructions

[0102] 614 sensor data 616 Stokes parameters

[0103] 618 optional polarization state of light

[0104] 620 angle of linear polarization

[0105] 622 degree of linear polarization

[0106] 624 predefined criterion

[0107] 626 look up table

[0108] 628 neural network

[0109] 630 fuzzy logic module

[0110] 632 driving surface status signal

[0111] 700 controlling the illuminating the illumination zone on the driving surface adjacent to the vehicle using the light source

[0112] 702 receiving the sensor data from the set of photo detector sensors

[0113] 704 calculating Stokes parameters descriptive of the scattered light using the sensor data

[0114] 706 calculating an angle of linear polarization from the Stokes parameters

[0115] 708 calculating a degree of linear polarization from the Stokes parameters

[0116] 710 determining a driving surface status signal by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion

[0117] 712 providing the driving surface status signal

Claims

ClaimsClaim 1. A vehicle sensor system (600) comprising an opto-electronic sensor (100), wherein the opto-electronic sensor comprises: a light source (102) configured for illuminating an illumination zone (304) on a driving surface (302) adjacent to a vehicle (300), wherein the light source is configured to generate near infrared linearly polarized light (206); a set of photo detector sensors (104) configured for providing sensor data (614) that is descriptive of scattered light (208) 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 specific 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 the vehicle sensor system further comprises: a memory (610) storing machine executable instructions (612); a computational system (604), wherein execution of the machine executable instructions causes the computational system to: receive (702) the sensor data (614) from the set of photo detector sensors; calculate (704) Stokes parameters (616) descriptive of the scattered light using the sensor data; calculate (706) an angle of linear polarization (620) from the Stokes parameters; calculate (708) a degree of linear polarization (622) from the Stokes parameters;determine (710) a driving surface status signal (632) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion; and provide (712) the driving surface status signal.Claim 2. The vehicle sensor system of claim 1, wherein the driving surface status signal is any one of the following: a status indicating ice detected on the driving surface; a status indicating water detected on the driving surface; and a status indicating a dry surface detected for the driving surface.Claim 3. The vehicle sensor system of claim 2, wherein if the driving surface status signal indicates water or ice on the driving surface then execution of the machine executable instructions further causes the computational system to perform any one of the following: issue a vehicle speed reduction command, issue an increase minimum distance to next vehicle command, issue an icy road warning using a user interface if the driving surface status indicates ice on the driving surface, and issue a wet road warning using the user interface if the driving surface status indicates water on the driving surface.Claim 4. The vehicle sensor system of any one of claims 1, 2, or 3, wherein the vehicle sensor system is configured to be mounted on a front surface of the vehicle, and wherein the illumination zone is in front of the vehicle.Claim 5. The vehicle sensor system of any one of claims 1, 2, or 3, wherein the vehicle sensor system is configured to be mounted on an underside (500) of the vehicle facing the driving surface.Claim 6. The vehicle sensor system of any one of the preceding claims, wherein the light source is any one of the following: a light emitting diode (200), a laser diode, and an illumination system of a Lidar system.Claim 7. The vehicle sensor system of any one of the preceding claims, wherein execution of the machine executable instructions further causes the computational system to: calculate a polarization state of light from the Stokes parameters; and compare the polarization state of light to the predetermined criteria also during determination of the driving surface status signal.Claim 8. The vehicle sensor system of any one of the preceding claims, wherein the opto-electronic sensor further comprises a set of lenses, each lens (210) being configured for focusing the scattered light onto a specific one of the set of photo detectors.Claim 9. A vehicle comprising the vehicle sensor system according to any one of the preceding claims.Claim 10. A method of operating a vehicle sensor system (600) comprising an optoelectronic sensor (100) according to any one of claims 1 through 8, wherein the method comprises: controlling (700) illumination of the illumination zone on the driving surface adjacent to the vehicle using the light source; receiving (702) the sensor data (614) from the set of photo detector sensors; calculating (704) the Stokes parameters (616) descriptive of the scattered light using the sensor data; calculating (706) the angle of linear polarization (620) from the Stokes parameters; calculating (708) the degree of linear polarization (622) from the Stokes parameters; determining (710) the driving surface status signal (632) by comparing the angle of linear polarization and the degree of linear polarization to the predetermined criterion; andproviding (712) the driving surface status signal.Claim 11. A computer program comprising machine executable instructions configured for controlling a computational system (604) to perform the method of claim 10.

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