Fog detection system

Abstract

Disclosed herein is a vehicle sensor system (400) comprising an opto-electronic sensor (100). The execution of machine executable instructions (412) causes a computational system (404) to: receive (502) sensor data (414) from a set of photo detector sensors (104); calculate (504) the Stokes parameters (416) descriptive of scattered light (208) using the sensor data; calculate (506) an angle of linear polarization (420) from the Stokes parameters; calculate (508) a degree of linear polarization (422) from the Stokes parameters; detect (510) fog (308) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion (424); and provide (512) a fog warning signal (432) if the fog is detected.

Description

[0001] FOG DETECTION SYSTEM

[0002] Description

[0003] Field of the invention

[0004] The invention relates to opto-electronic sensors, in particular to opto-electronic sensors configured for detecting fog.

[0005] Background and related art

[0006] When driving

[0007] Summary

[0008] 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.

[0009] In one aspect the invention provides for a vehicle sensor system comprising an optoelectronic sensor. The opto-electronic sensor comprises a polarized light source configured for illuminating a volume located in front of an exterior surface of a windshield of a vehicle. 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 volume by the set of photo detector sensors. The vehicle sensor system further 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. 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 detect fog by comparing the 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 a fog warning signal if the fog is detected.

[0010] In another aspect the invention provides for a vehicle comprising the windshield and the vehicle sensor system according to an embodiment.

[0011] 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 illuminating the volume using the polarized 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 detecting fog by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion. The method further comprises providing a fog warning signal if the fog is detected. In another aspect the invention provides for a computer program comprising machine executable instructions configured for controlling a computational system to perform the method of operating the vehicle sensor system.

[0012] Brief description of the drawings

[0013] In the following embodiments of the invention are explained in greater detail, by way of example only, making reference to the drawings in which:

[0014] Fig. 1 shows a top view of an opto-electronic sensor;

[0015] Fig. 2 shows a side view of an opto-electronic sensor;

[0016] Fig. 3 illustrates the opto-electronic sensor in operation;

[0017] Fig. 4 illustrates an example of a vehicle sensor system; and

[0018] Fig. 5 shows a flow chart which shows a method of operating the vehicle sensor system of Fig. 4.

[0019] Detailed Description

[0020] 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.

[0021] In an example, a vehicle sensor system comprises an opto-electronic sensor. The optoelectronic sensor comprises a polarized light source configured for illuminating a volume located in front of an exterior surface of a windshield of a vehicle. In some examples the polarized light source may be a linearly polarized infra-red light source. Using an infra-red light source may have the benefit of it not being visible to occupants or drivers of the vehicle or other vehicles.

[0022] 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 volume located in front of the exterior surface of the windshield by the set of photo detector sensors. The distance between the volume in front of the windshield and the windshield may vary depending upon the configuration of the light source and the set of photo detector sensors. The distance could for example range between several millimeters in front of the windshield to a meter or even tens of meters. For example, a brighter light source or a light source focused and / or collimated with a lens may enable the volume to be further away from the windshield. By the same token the use of a lens to focus light into individual photo detector sensor could increase the amount of scattered light detected by individual photo detector sensors and enhance measurement from a volume more distant to the windshield.

[0023] 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 specific one of the set of photo detectors. The set of linear polarizer filters comprises filters having a respective polarization axis that is 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.

[0024] 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 the linear polarization from the Stokes parameters. Execution of the machine-executable instructions further causes the computational system to detect fog by comparing the 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 a fog warning signal if the fog is detected. This example may be beneficial because it may provide for an automatic means of detecting fog by a vehicle. This may be useful for example for warning an operator to decrease speed. It may also be useful in automatically engaging or operating various functions of a vehicle such as to engage fog lights or send control signals to an automated driving system to ensure that there is a sufficient spacing between vehicles. In some examples the fog warning signal may also refer to the detection of dust, rain, snow, smoke, or other particulates or material which may restrict the view or vision of the driver.

[0025] In another example, if the fog warning signal is provided execution of the machineexecutable instructions further causes the computational system to perform any one of the following: generate a brightness change command for a HUD or heads up display of a windshield, generate fog warning display commands for the HUD, generate a fog light activation command, generate reduced speed commands, and generate user interface warning commands. All of these actions may be beneficial because they may provide for automatic operations by a vehicle which make it safer or which provide instructions for an operator to follow.

[0026] In another example, the polarized light source is configured for providing linearly polarized light for the illumination of the volume.

[0027] In another example, the polarized light source is configured for providing near infrared linearly polarized light for the illumination of the volume.

[0028] In another example, the opto-electronic sensor can be configured for being optically coupled to the windshield. This may be beneficial because it may eliminate the effect of ice or moisture on the inner surface of the windshield. The opto-electronic sensor may be optically coupled to the interior surface of the windshield. Optical coupling as used herein encompasses coupling one or more optical components of the opto-electronic sensor such that they do not have an air gap between that component and the interior surface of the windshield. For example, the polarized light source and / or the set of photodetector sensor may be optically coupled to the interior surface of the windshield. The optical coupling may be implemented in different ways. In one example an epoxy or other optical coupling medium may be used to for the optical coupling. In other examples light guides may be used by using them to connect the optical component and the interiors surface of the windshield.

[0029] In another example, the vehicle sensor system further comprises the vehicle windshield.

[0030] In another example, execution of the machine-executable instructions further causes the computational system to receive windshield wiper timing data. Execution of the machineexecutable instructions further causes the computational system to control reception of the sensor data from the set of photo detector sensors using windshield wiper timing data such that the effects of water on the exterior surface of the windshield is minimized. For example, when it is raining or there is some other water which is on the surface of the windshield such as mist, it may obscure the measurement of the scattered light. However, when the windshield wipers are activated for a particular period of time, the view of the sensors to the volume may be clear. This example may provide for an improved means of detecting fog. In a further example, the opto-electronic sensor is located inside of the vehicle and is viewing the volume from within the vehicle and through the windshield.

[0031] 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 light to a further predetermined criterion for detection of the fog. This example may be beneficial because the polarization state of light is an additional measured quantity which can be used for the detection of fog.

[0032] In another example, the opto-electronic sensor further comprises a set of lenses. Each lens being configured for focusing the scattered light onto a specific one of the set of photo detectors. This example may be beneficial because these individual lenses can be used to gather additional light and focus them onto particular photo detectors. This may provide for enhanced or improved fog detection.

[0033] In another example, a vehicle comprises the windshield and the vehicle sensor system according to an example. This may be beneficial because it may provide for a vehicle which is able to automatically detect fog and, in some cases, automatically adapt to this.

[0034] In another example, the opto-electronic sensor is located in any one of the following locations: incorporated into a rearview mirror of the vehicle, mounted at least partially within a dashboard of the vehicle, and optically coupled to the windshield.

[0035] 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.

[0036] 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. 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).

[0037] 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:

[0038] So= l(x) + l(y)

[0039] 51 = l(x) - l(y)

[0040] 52= I (+45°) - 1 (-45°)

[0041] 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.

[0042] It may be also shown that for partially polarized light

[0043] S02> Sf + Sf + S32while for a well polarized (coherent) light

[0044] S02= S? + Sf + S32

[0045] 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. From the Stokes parameters one can calculate other parameters. The Polarization state of light (PSoL) is:

[0046] PSoL

[0047] The Angle of linear polarization AoLP is either of the following two equations:

[0048] AoLP

[0049] AoLP = arctan

[0050] The Degree of linear polarization (DoLP) is:

[0051] DoLP

[0052] 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 light. In some examples the LED emits near infrared light. This light is then focused by the lens 202 which then goes through a polarizer filter 204 to produce linearly polarized light 206. This linearly polarized light is then directed at volume located in front of an exterior surface of a windshield of a vehicle. Some of this light that enters this volume 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 laser or infrared laser, in which case the polarizer filter 204 and the lens 202 may not be necessary.

[0053] Fig. 3 illustrates the use of the opto-electronic sensor 100 to detect fog 308. There is a windshield 300 with an interior surface 302 and an exterior surface 304. Within the interior surface 302 there is an opto-electronic sensor 100. It sends polarized light 206 to a volume located in front of the exterior surface 304 of the windshield 300. Within the volume 306 is a fog 308. The polarized light 206 entering the volume 306 is scattered by the fog 308. Some of the light is scattered back as scattered light 208 which enters the set of photo detector sensors. The fog 308 can be detected by the angle of linear polarization and the degree of linear polarization as determined by sensor data measured by the set of photo detector sensors 104.

[0054] Fig. 4 illustrates an example of a vehicle sensor system 400. There is a windshield 300 with an interior surface 302 and exterior surface 304 again. The opto-electronic sensor 100 faces the interior surface 302 and shines a polarized light 206 into the volume 306. Any fog there will cause scattered light 208 to go to the set of photo detector sensors 104.

[0055] Fig. 5 illustrates an example of a vehicle sensor system 500. The vehicle sensor system 500 could for example be integrated into the example illustrated in Fig. 4. In this example, the opto-electronic sensor 100 is shown as shining polarized light 206 in volume 306. 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 406 of a control unit 402.

[0056] The control unit 402 is shown as having a computational system 404 that is in communication with the sensor interface 406, a memory 410 and optionally a vehicle communication interface 408. The memory 410 is intended to represent various types of memory which may be accessible to the computational system 404. The vehicle communication interface 408 may enable the computational system 404 to send various messages and commands and receive data from other components to a vehicle.

[0057] The memory 410 is shown as containing machine-executable instructions 412. The machine-executable instructions 412 enable the computational system 404 to perform various numerical and control tasks. The memory 410 is further shown as containing sensor data 414 that has been received from the opto-electronic sensor 100. The memory 410 is further shown as containing Stokes parameters 416 that have been calculated from the sensor data 414. The memory 410 is further shown as optionally containing the polarization state of light 418 that has been calculated from the Stokes parameters 416. The polarization state of light 418 may be optionally used when detecting fog. The memory 410 is further shown as containing the angle of linear polarization calculated from the Stokes parameters 416.

[0058] The memory 410 if further shown as containing the degree of linear polarization calculated from the Stokes parameters 416. The memory 410 if further shown as containing a predefined criterion 424 against which the angle of linear polarization 420, the degree of linear polarization 422, and optionally the polarization state of light to detect if fog 308 is present in the volume 306. The memory is further shown as containing the fog warning signal 432 that was determined by comparing at least the angle of linear polarization 420 and the degree of linear polarization 422 against the predefined criterion 424. The predefined criterion 424 may be supplied in a variety of ways. The memory 410 is further shown as containing a lookup table 426 which may be used to provide the predefined criterion 424. In other examples, a neural network 428 or a fuzzy logic module 430 may also be used.

[0059] The neural network 428 could for example contain several fully connected layers and receive as input the polarization state of light (optionally), the angle of linear polarization 420, and the degree of linear polarization 422. The output may then be the actual fog warning signal 432. The neural network 428 could be trained by acquiring data from when there are differing amounts of fog in the volume 306 and labeling the measured angle of linear polarization 420 and degree of linear polarization 422 and then using this data as training data.

[0060] As a further a fuzzy logic module 430 which also takes as input the polarization state of light (optionally), the angle of linear polarization 420, and the degree of linear polarization 422. and outputs the fog warning signal 432.

[0061] Fig. 5 shows a flowchart which illustrates a method of operating the vehicle sensor system 400 of Fig. 4. In step 500, the illumination of the volume 306 located in front of the exterior surface 304 of the windshield 300 is controlled using the polarized light source 102. In step 502, the sensor data 414 is received from the set of photo detector sensors 104. In step 504, the Stokes parameters 416 are calculated using the sensor data 414. In step 506, the angle of linear polarization 420 is calculated from the Stokes parameters 416. In step 508, the degree of linear polarization 422 is calculated from the Stokes parameters 416. In step 510, fog is detected by comparing the angle of linear polarization 420 and the degree of linear polarization 422 to the predetermined criterion 424. In step 512, the fog warning signal 432 is provided if the fog is detected.

[0062] 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.

[0063] 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.

[0064] 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.

[0065] 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.

[0066] 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).

[0067] 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.

[0068] 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.

[0069] 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.

[0070] 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. List of Reference Numerals

[0071] 100 opto-electronic sensor

[0072] 102 polarized light source

[0073] 104 set of photo detector sensors

[0074] 106 reference polarization axis

[0075] 108 first linear polarizer filter at 0°

[0076] 110 second linear polarizer filter at 45°

[0077] 112 third linear polarizer filter at 90°

[0078] 114 fourth linear polarizer filter at 135°

[0079] 200 LED

[0080] 202 lens

[0081] 204 polarizer filter

[0082] 206 polarized light

[0083] 208 scattered light

[0084] 208' concentrated scattered light

[0085] 210 lens

[0086] 300 windshield

[0087] 302 interior surface of windshield

[0088] 304 exterior surface of windshield

[0089] 306 volume

[0090] 308 fog

[0091] 400 vehicle sensor system

[0092] 402 control unit

[0093] 404 computational system

[0094] 406 sensor interface

[0095] 408 vehicle communication interface

[0096] 410 memory

[0097] 412 machine executable instructions

[0098] 414 sensor data 416 Stokes parameters

[0099] 418 optional polarization state of light

[0100] 420 angle of linear polarization

[0101] 422 degree of linear polarization

[0102] 424 predefined criterion

[0103] 426 look up table

[0104] 428 neural network

[0105] 430 fuzzy logic module

[0106] 432 fog warning signal

[0107] 500 controlling the illumination the volume located in front of an exterior surface of windshield of a vehicle using the polarized light source

[0108] 502 receive the sensor data from the set of photo detector sensors

[0109] 504 calculate Stokes parameters descriptive of the scattered light using the sensor data

[0110] 506 calculate an angle of linear polarization from the Stokes parameters

[0111] 508 calculate a degree of linear polarization from the Stokes parameters

[0112] 510 detect fog by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion

[0113] 512 provide a fog warning signal if the fog is detected

Claims

ClaimsClaim 1. A vehicle sensor system (400) comprising an opto-electronic sensor (100), wherein the opto-electronic sensor comprises: a polarized light source (102) configured for illuminating a volume (306) located in front of an exterior surface (304) of a windshield (300) of a vehicle; a set of photo detector sensors (104) configured for providing sensor data (414) that is descriptive of scattered light (208) received from the volume by the set of photo detector sensors; 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, 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); a memory (410) storing machine executable instructions (412); a computational system (404), wherein execution of the machine executable instructions causes the computational system to: receive (502) the sensor data from the set of photo detector sensors; calculate (504) Stokes parameters (416) descriptive of the scattered light using the sensor data; calculate (506) an angle of linear polarization (420) from the Stokes parameters; calculate (508) a degree of linear polarization (422) from the Stokes parameters; detect (510) fog (308) by comparing the angle of linear polarization and the degree of linear polarization to a predetermined criterion (424); and provide (512) a fog warning signal (432) if the fog is detected.Claim 2. The vehicle sensor system of claim 1, wherein if the fog warning signal is provided execution of the machine executable instructions further causes the computational system to perform any one of the following: generate a brightness change command for a HUD of the windshield, generate a fog warning display command for the HUD, generate a fog lite activation command, generate reduced speed commands, and generate user interface warning commands.Claim 3. 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 volume.Claim 4. The vehicle sensor system of any one of the preceding claims, wherein the opto-electronic sensor is configured for being optically coupled to an interiors furface (302) of the windshield.Claim 5. The vehicle sensor system of any one of the preceding claims, wherein the vehicle sensor system further comprises the vehicle windshield.Claim 6. The vehicle sensor system of any one of the preceding claims, wherein execution of the machine executable instructions further causes the computational system to: receive windshield wiper timing data; and control reception of the sensor data from the set of photo detector sensors using the windshield wiper timing data such that effects of water on the exterior surface of the windshield is minimized.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; andcompare the polarization state of light to a further criterion for detection of the fog.Claim 8. The vehicle sensor system of any one of the preceding claims, wherein the opto-electronic sensor further comprises a set of lenses (210), each lens being configured for focusing the scattered light onto a specific one of the set of photo detectors.Claim 9. A vehicle comprising the windshield and the vehicle sensor system according to any one of the preceding claims.Claim 10. The vehicle of claim 9, wherein the opto-electric sensor is located in any one of the following locations: incorporated into a rear-view mirror of the vehicle, mounted at least partially within a dashboard of the vehicle, and optically coupled to the windshield.Claim 11. A method of operating a vehicle sensor system (400) comprising an optoelectronic sensor (100) according to any one of claims 1 through 8, wherein the method comprises: controlling (500) the illumination of the volume (306) using the polarized light source; receiving (502) the sensor data (414) from the set of photo detector sensors; calculating (504) the Stokes parameters (416) descriptive of the scattered light using the sensor data; calculating (506) the angle of linear polarization (420) from the Stokes parameters; calculating (508) the degree of linear polarization (422) from the Stokes parameters; detecting (510) fog by comparing the angle of linear polarization and the degree of linear polarization to the predetermined criterion (424); and providing (512) the fog warning signal (432) if the fog is detected.Claim 12. A computer program comprising machine executable instructions (412) configured for controlling a computational system (404) to perform the method of claim 11.

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