Photosensor system for monitoring windshield of vehicle

Abstract

The invention discloses a vehicle sensor system including a photosensor. The photosensor includes a polarized light source (102) configured to illuminate a windshield of the vehicle within an illumination area, where the illumination area is above the photosensor. The photosensor also includes a set of photodetector sensors (104) configured to provide sensor data describing scattered light received by the set of photodetector sensors from the illuminated area. The photosensor also includes a set of linear polarizer filters (108, 110, 112, 114). Each filter is configured for filtering scattered light before the scattered light reaches a respective one of the set of light detectors. The set of linear polarizer filters includes filters having respective polarization axes rotated relative to a reference polarization axis (106) 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).

Description

Technical Field

[0001] The present invention relates to photoelectric sensors, and in particular to a photoelectric sensor configured for monitoring the windshield of a vehicle. Background Art

[0002] Vehicle windshields protect the driver and passengers during vehicle motion. However, they can become coated with condensation or water, which can obscure the driver's field of view and interfere with the head-up display (HUD). Summary of the Invention

[0003] The invention provides a vehicle sensor system, a vehicle, a method and a computer program in the independent claims. Embodiments are given in the dependent claims.

[0004] In one aspect, the present invention provides a vehicle sensor system including a photosensor. The photosensor includes a polarized light source configured to illuminate a vehicle's windshield within an illumination area. The illumination area is above the photosensor. The photosensor also includes a set of photodetector sensors configured to provide sensor data describing scattered light received by the set of photodetector sensors from the illumination area. The photosensor also includes a set of linear polarizer filters. Each of the set of linear polarizer filters is configured to filter the scattered light before it reaches a corresponding one of the set of photodetectors. The set of linear polarizer filters includes filters having respective polarization axes nominally rotated by 0°, 45°, 90°, and 135° relative to a reference polarization axis. The values of 0°, 45°, 90°, and 135° represent optional angular rotations for various polarization filters. To function, the filters do not need to be at precisely these angular rotations. Changing the angle by + or -2.5° will still allow the photosensor to function properly. For example, a first linear polarizer filter can be positioned between -2.5° and +2.5° relative to a reference polarization axis. A second polarization filter can be positioned, for example, between 42.5° and 47.5° relative to the reference polarization axis. A third linear polarization filter can be positioned, for example, between 87.5° and 92.5° relative to the reference polarization axis. A fourth linear polarization filter can be positioned, for example, between 132.5° and 137.5° relative to the reference polarization axis. As used herein, a reference polarization axis is an arbitrarily rotated polarization axis that is nominally set to match the desired angular position of the first polarization filter.

[0005] This embodiment may have the following benefits: It provides an integrated package for acquiring sensor data describing scattered light originating from a polarized light source.The polarized light source is positioned to illuminate an illumination area, and the set of light detector sensors is configured to measure light scattered from the illumination area.

[0006] In another embodiment, the vehicle sensor system further includes a memory storing machine-executable instructions. The vehicle sensor system further includes a computing system. Execution of the machine-executable instructions causes the computing system to receive the sensor data from the set of light detector sensors. Execution of the machine-executable instructions further causes the computing system to use the sensor data to calculate Stokes parameters describing scattered light. Execution of the machine-executable instructions further causes the computing system to optionally calculate a polarization state of the light based on the Stokes parameters.

[0007] This embodiment may be beneficial because it may provide a photosensor that may be used to determine the presence of liquid or solid water (such as water, fog, or ice) on a windshield using Stokes parameters.

[0008] Execution of the machine-executable instructions further causes the computing system to calculate the angle of linear polarization based on the Stokes parameters. Execution of the machine-executable instructions further causes the computing system to calculate the degree of linear polarization based on the Stokes parameters. Execution of the machine-executable instructions further causes the computing system to determine a windshield status signal by comparing the polarization state (optionally), the angle of linear polarization, and the degree of linear polarization of the light to predetermined criteria. For example, the windshield status signal may be compared to a lookup table of values, which may then be used to assign the windshield status signal. Execution of the machine-executable instructions also causes the computing system to provide the windshield status signal. The windshield status signal may, for example, be used to provide a signal to the vehicle operator. In other cases, the windshield status signal may be provided to an onboard computer system to modify the vehicle's behavior, such as causing it to activate window defrosting or to cause other actions, such as reducing the intensity of a heads-up display.

[0009] In another embodiment, the windshield status signal is a status indicating that ice is detected on the windshield.

[0010] In another embodiment, the windshield status signal is a status indicating that liquid has been detected on the windshield. This may be, for example, the detection of water.

[0011] In another embodiment, the windshield status signal is a dry windshield status indicating the windshield. This may be useful because it may be used to indicate that there is neither ice nor liquid condensed on the windshield.

[0012] In another embodiment, if the windshield status is a status indicating ice has been detected on the windshield or a status indicating liquid has been detected on the windshield, the windshield status signal further includes any one of: a brightness change command for a head-up display (HUD) for the windshield, a system deactivation command for the windshield HUD, an ice warning, a humidity warning, and a windshield defrost command. This embodiment may be beneficial because any of these commands can be used to automatically modify the behavior of the vehicle's automated systems in response to the detection of ice or liquid on the windshield to automatically remedy the obstructed view.

[0013] In another embodiment, the polarized light source is adapted to provide linearly polarized light for illumination of the illumination area. This may be beneficial as it may be used to provide a clearer distinction between an icy windscreen, a wet windscreen and a dry windscreen.

[0014] In another embodiment, the polarized light source has a light source polarization axis that is rotated 45° relative to a reference polarization axis. This embodiment may be beneficial because it provides a polarized light source that can provide sensor data that can clearly distinguish between dry, wet, and iced windshields.

[0015] In another embodiment, the illumination area is 1 cm to 10 cm away from the photosensor.

[0016] In another embodiment, the illumination area is 2 cm to 7 cm from the photosensor. This embodiment can be beneficial because it enables the sensor to be placed near or around the windshield, but not directly against it. This can, for example, enable the photosensor to be placed in the dashboard of a vehicle. Due to the close distance between the sensor and the windshield, the risk of obstructing the sensor by objects, such as sunglasses or other objects on the dashboard, coming between the sensor and the windshield is reduced. This reduced chance of obstruction can provide more reliable results.

[0017] In another embodiment, the polarized light source comprises an infrared light source. The use of an infrared light source may be beneficial because it will not be visible to the operator of the vehicle and will not disturb or even blind the operator when the light source is activated.

[0018] 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.

[0019] In another embodiment, the infrared light source is a solid-state infrared laser. This can be advantageous because it can be very compact and provides a means of illuminating a very small portion of the windshield. This can be relevant in situations where other IR-based tools are operated in the vehicle, such as IR detectors for traffic detection, such as thermal imaging or infrared detectors. Using a laser can minimize any potential negative effects, such as those caused by scattered IR light.

[0020] Another aspect of the invention is a head-up display comprising a vehicle sensor system according to the above description.

[0021] In another embodiment, the vehicle sensor system further comprises a vehicle windshield. The vehicle windshield is located within the lighting area.

[0022] In another embodiment, the polarized light source is configured such that it has an angle of incidence with the windshield between 15° and 75°.

[0023] In another embodiment of the vehicle sensor system, the vehicle sensor system further comprises a head-up display having a housing, wherein the head-up display comprises a photoelectric sensor or a portion thereof. The head-up display is configured to project an image onto a black panel in or on the windshield to provide information to the driver or other passengers of the vehicle. By combining the photoelectric sensor with the head-up display, it is advantageously possible to check whether the area of the windshield containing information for the driver is capable of correctly displaying the information. Advantageously, the vehicle sensor system can detect icing, dust, and / or fogging of the information area, and the head-up display can operate more reliably. The head-up display can also comprise only a collection of polarized light sources or light detector sensors that are part of the photoelectric sensor.

[0024] In another embodiment of the vehicle sensor system, at least the set of photodetector sensors is located inside or outside the housing of the head-up display. This means that at least the set of photodetector sensors is arranged inside the head-up display so that the windshield, or a portion thereof (at least the area of the windshield containing information for the driver or other passengers), is visible to the set of photodetector sensors. Preferably, the set of photodetector sensors is arranged inside or outside the optical path of the head-up display. The optical path of a head-up display refers to the path taken by light from the head-up display's internal display to the windshield within the housing of the head-up display to project information onto the windshield. Alternatively, the set of photodetectors is arranged outside the housing of the head-up display, meaning that the set of photodetectors is arranged on an outer surface of the housing or is part of the housing. Similar arrangements inside or outside the housing are also possible for complete photosensors or simply polarized light sources.

[0025] In another embodiment of the vehicle sensor system, the head-up display includes a polarized light source, preferably the light source of the head-up display's internal TFT display, thereby serving as the polarized light source for the photosensor. This feature advantageously allows the head-up display's light source to additionally serve as the polarized light source for the sensor, eliminating the need for an additional light source. A collection of light detectors, arranged internally or externally to the housing, detects light reflected from the windshield from the head-up display, enabling assessment of the windshield's condition, such as whether it is clear, icy, dusty, or fogged.

[0026] 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 photosensor is positioned alongside the head-up display's projected output. The head-up display's projected output is an opening in the housing, through which the head-up display's light is emitted to project the image onto the windshield. In this embodiment, the photosensor, or a portion thereof, is positioned alongside the opening in the housing. Preferably, the photosensor is positioned directly adjacent to the opening or at a distance therefrom, preferably from 2 mm to 80 mm. Preferably, the photosensor is positioned on the edge surrounding the housing opening (and, accordingly, the projected output).

[0027] In another embodiment of the vehicle sensor system, the photoelectric sensor is positioned side-by-side with the display of a head-up display. This configuration is particularly useful for so-called black panel head-up displays, which project an image directly from the display onto a black panel on the windshield. The display is mounted in an opening in the instrument panel to project the image onto the windshield. Due to the side-by-side arrangement of the display and sensor, the photoelectric sensor is able to detect the status of the windshield through the same opening in the instrument panel.

[0028] In another embodiment, a vehicle windshield includes a frit strip. This frit strip can also be referred to as a black coating. For example, the frit strip is a strip of black enamel baked into the edge of the windshield. It is used to bond the windshield to the vehicle. A photoelectric sensor is positioned relative to the vehicle windshield such that the illuminated area is within the frit strip. This embodiment can be beneficial because the illumination occurs in a location that is unrelated to potential limitations on the vehicle operator's field of view due to technical components. The strip forms an area that is essentially unrelated to the driver's field of view, so any components of the sensor system located there do not affect the operator. Furthermore, because the frit strip is transparent to infrared light, for example, an infrared light source can be used to detect ice or condensation on the windshield through the frit strip.

[0029] In another embodiment, the vehicle includes an instrument panel. The photoelectric sensor is at least partially mounted within the instrument panel. This embodiment can be advantageous because it provides a location for mounting the photoelectric sensor. Thus, it can be implemented in a simple manner within the vehicle, for example, without the need for complex routing of additional cables to operate the sensor system. In the instrument panel area, a large number of cable harnesses are already present, simplifying the wiring of the system.

[0030] In another aspect, the present invention provides a vehicle comprising a windscreen and a vehicle sensor system according to any one of the preceding claims. This embodiment may be beneficial in that the vehicle will have means of detecting the presence of ice or condensation on the windows.

[0031] In another aspect, the present invention provides a method for operating a vehicle sensor system. The vehicle sensor system includes a photosensor. The photosensor includes a polarized light source configured to illuminate a vehicle windshield within an illumination area. The illumination area is above the photosensor. The photosensor also includes a set of photodetector sensors configured to provide sensor data describing scattered light received by the set of photodetector sensors from the illumination area. The photosensor further includes a set of linear polarizer filters, each filter configured to filter the scattered light before it reaches a corresponding one of the set of photodetectors. The first linear filter will have an orientation between -2.5° and 2.5° relative to a reference polarization axis. The second filter will have an orientation between 42.5° and 47.5° relative to the reference polarization axis. The third filter will have an orientation between 87.5° and 92.5° relative to the reference polarization axis. The fourth filter will have an orientation between 132.5° and 137.5° relative to the reference polarization axis.

[0032] The method includes receiving sensor data from a collection of light detector sensors. The method also includes calculating Stokes parameters describing the scattered light using the sensor data. The method also includes optionally calculating the polarization state of the light based on the Stokes parameters. The method further includes calculating the angle of linear polarization from the Stokes parameters. The method also includes calculating the degree of linear polarization based on the Stokes parameters. The method also includes determining a windshield condition by comparing the polarization state (optionally), the angle of linear polarization, and the degree of linear polarization of the light to predetermined criteria. The method also includes providing a windshield condition signal. This signal can be provided to the vehicle operator, or it can be provided to the vehicle's computer or control system to perform an automated action, such as defrosting the windows or reducing the brightness or intensity of the head-up display (HUD).

[0033] In another aspect, the invention provides a computer program comprising machine-executable instructions for execution by a computing system configured to control a vehicle sensor system.The computer program may, for example, be stored on a non-transitory storage medium.

[0034] A vehicle sensor system includes a photosensor. The photosensor includes a polarized light source configured to illuminate a vehicle's windshield within an illumination area. The illumination area is above the photosensor. The photosensor also includes a set of photodetector sensors configured to provide sensor data describing scattered light received by the set of photodetector sensors from the illumination area. The photosensor also includes a set of linear polarizer filters. Each filter is configured to filter the scattered light before it reaches a corresponding one of the set of photodetectors. The first filter has an orientation between -2.5° and 2.5° relative to a reference polarization axis. The second linear polarization filter has an orientation between 42.5° and 47.5° relative to the reference polarization axis. The third linear polarization filter has an orientation between 87.5° and 92.5° relative to the reference polarization axis. The fourth linear polarization filter has an orientation between 132.5° and 137.5° relative to the reference polarization axis.

[0035] Execution of the machine-executable instructions causes the computing system to receive sensor data from the collection of light detector sensors. Execution of the machine-executable instructions further causes the computing system to use the sensor data to calculate Stokes parameters describing the scattered light. Execution of the machine-executable instructions further causes the computing system to optionally calculate the polarization state of the light based on the Stokes parameters. Execution of the machine-executable instructions further causes the computing system to calculate the angle of linear polarization based on the Stokes parameters. Execution of the machine-executable instructions further causes the computing system to calculate the degree of linear polarization based on the Stokes parameters. Execution of the machine-executable instructions further causes the computing system to determine a windshield status signal by comparing the polarization state (optionally), the angle of linear polarization, and the degree of linear polarization of the light to predetermined criteria. Execution of the machine-executable instructions further causes the computing system to provide the windshield status signal.

[0036] As will be appreciated by those skilled in the art, aspects of the present invention may be embodied as devices, methods, or computer program products. Thus, aspects of the present invention may take the form of entirely hardware embodiments, entirely software embodiments (including firmware, resident software, microcode, etc.), or embodiments combining software and hardware aspects, all of which may generally be referred to herein as "circuits," "modules," or "systems." Furthermore, aspects of the present invention may take the form of a computer program product embodied in one or more computer-readable media having computer-executable code embodied thereon.

[0037] Any combination of one or more computer-readable media may be utilized. A computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. As used herein, "computer-readable storage medium" encompasses any tangible storage medium that can store instructions that can be executed by a processor or computing system of a computing device. A computer-readable storage medium may be referred to as a computer-readable, non-transitory storage medium. A 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 capable of storing data that can be accessed by the computing system of the computing device. Examples of computer-readable storage media include, but are not limited to, floppy disks, magnetic hard drives, solid-state drives, flash memory, USB thumb drives, random access memory (RAM), read-only memory (ROM), optical disks, magneto-optical disks, and a computing system's register file. Examples of optical disks include compact disks (CDs) and digital versatile disks (DVDs), such as CD-ROMs, CD-RWs, CD-Rs, DVD-ROMs, DVD-RWs, or DVD-Rs. The term computer-readable storage medium also refers to various types of recording media that can be accessed by a computing device via a network or communication link. For example, data can be retrieved via 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, wireline, optical fiber cable, RF, etc., or any suitable combination of the foregoing.

[0038] A computer-readable signal medium may include a propagated data signal containing computer-executable code, 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 electromagnetic, 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 conjunction with an instruction execution system, apparatus, or device.

[0039] "Computer memory" or "memory" is an example of a computer-readable storage medium. Computer memory is any memory directly accessible to a computing system. "Computer storage" or "storage" is another 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, and vice versa.

[0040] As used herein, a "computing system" encompasses an electronic component capable of executing a program or machine-executable instructions or computer-executable code. References to computing systems including examples of a "computing system" should be interpreted as potentially including more than one computing system or processing core. A computing system may, for example, be a multi-core processor. A computing system may also refer to a collection of computing systems within a single computer system or distributed across multiple computer systems. The term computing system should also be interpreted as potentially referring to a collection or network of computing devices, each of which includes a processor or computing system. Machine-executable code or instructions may be executed by multiple computing systems or processors, which may be within the same computing device or even distributed across multiple computing devices.

[0041] Machine executable instructions or computer executable code may include instructions or programs that cause a processor or other computing system to perform aspects of the present invention. Computer executable code for performing operations for various aspects of the present invention may be written in any combination of one or more programming languages, including object-oriented programming languages such as Java, Smalltalk, C++, 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 precompiled form and may be used in conjunction with an interpreter that generates 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 a programmable logic gate array.

[0042] 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 case, 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 may be connected to an external computer (e.g., through the Internet using an Internet service provider).

[0043] Various 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 present invention. It should be understood that each block or portion of a block in the flowcharts, illustrations, and / or block diagrams may be implemented, where applicable, by computer program instructions in the form of computer-executable code. It should also be understood that combinations of blocks in different flowcharts, illustrations, and / or block diagrams may be combined, when not mutually exclusive. These computer program instructions may be provided to a computing system of a general-purpose computer, a special-purpose computer, or other programmable data processing device to produce a machine, such that the instructions, executed by the computing system of the computer or other programmable data processing device, create a device for implementing the functions / actions specified in one or more blocks of the flowcharts and / or block diagrams.

[0044] These machine-executable instructions or computer program instructions may also be stored in a computer-readable medium, which may instruct a computer, other programmable data processing apparatus, or other device to function in a specific manner so that the instructions stored in the computer-readable medium produce an article of manufacture including instructions for implementing the functions / actions specified in one or more blocks of the flowchart and / or block diagram.

[0045] Machine-executable instructions or computer program instructions may also be loaded onto a computer, other programmable data processing apparatus, or other device, so that a series of operational steps are performed on the computer, other programmable apparatus, or other device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable apparatus provide a process for implementing the functions / actions specified in one or more boxes of the flowchart and / or block diagram.

[0046] As used herein, a "user interface" is an interface that allows a user or operator to interact with a computer or computer system. A "user interface" may also be referred to as a "human-computer interface device." A user interface can provide information or data to an operator and / or receive information or data from an operator. A user interface can enable input from an operator to be received by a computer, and can provide output from the computer to a user. In other words, a user interface can allow an operator to control or manipulate a computer, and the interface can allow the computer to indicate the effects of the operator's controls or manipulations. The display of data or information on a display or graphical user interface is an example of providing information to an operator. Receiving data via a keyboard, mouse, trackball, touchpad, pointing stick, graphics tablet, joystick, game controller, webcam, headset, pedal, wired gloves, remote control, and accelerometer are all examples of user interface components that enable receiving information or data from an operator. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] In the following, embodiments of the invention are explained in more detail, by way of example only, with reference to the accompanying drawings, in which:

[0048] Figure 1 shows a top view of a photosensor;

[0049] Figure 2 shows a photoelectric sensor in operation;

[0050] Figure 3 shows an example of a vehicle sensor system; and

[0051] Figure 4 A flow chart is shown, which shows the operation Figure 3 Method for a vehicle sensor system. DETAILED DESCRIPTION

[0052] Elements with the same number in these figures are equivalent elements or perform the same function. If the function is equivalent, elements that have been discussed previously will not necessarily be discussed in the following figures.

[0053] Figure 1 A top view of a photosensor 100 for a vehicle sensor system is shown. Photosensor 100 is shown as comprising a collection of polarized light sources 102 and photodetector sensors. In this case, there are four photodetector sensors. A reference polarization axis 106 is present. A first linear polarizer filter 108 is present, set at 0° relative to reference polarization axis 106. A second linear polarizer filter 110 is present, set at 45° relative to reference polarization axis 106. A third linear polarizer filter 112 is present, set at 90° relative to reference polarization axis 106. A fourth linear polarizer filter 114 is present, set at 135° relative to reference polarization axis 106. In one example, polarized light 102 has a polarization axis that is aligned with any one of linear polarizer filters 108, 110, 112, 114. A photodetector is present beneath each of linear polarizer filters 108, 110, 112, 114.

[0054] The set of these light detector sensors 104 in combination with the linear polarizer filters 108, 110, 112, 114 enables the measurement of the Stokes parameters SO, Sl, S2 and S3. From these first four parameters, S4 and S5 related to the circular polarization can be calculated.

[0055] The signal measured by the photodiode will provide values of the intensity I at different polarization angles: I(x) (measured at 0° relative to the reference polarization axis 106), I(+45°) (measured at 45° relative to the reference polarization axis 106), I(y) (measured at 90° relative to the reference polarization axis 106), and I(-45°) (measured at 135° relative to the reference polarization axis 106).

[0056] From this, the Stokes parameters S0, S1, S2, and S3 can be derived. The Stokes formula describes the polarization state of light (PSoL) by using the following four basic parameters measured experimentally, for example, for a wave propagating along the z-axis:

[0057] S0=I(x)+I(y)

[0058] S1=I(x)-I(y)

[0059] S2=I(+45°)-I(-45°)

[0060] S3=I(RHC)-I(LHC)

[0061] where I(x), I(y), I(+45°), and I(-45°) are the intensities of the polarization components of light along the x, y, +45°, and -45° directions, respectively, as described above; and I(RHC) and I(LHC) are the intensities of the right-handed circularly (RHC) and left-handed circularly (LHC) polarization components of light.

[0062] It can also be shown that for partially polarized light,

[0063]

[0064] For well-polarized (coherent) light

[0065]

[0066] Therefore, by measuring the first three components (S0, S1, and S2), if the light is polarized, the last component (S3) can also be found. Otherwise, the value of S3 can only be roughly estimated.

[0067] Based on the Stokes parameters, other parameters can be calculated. The polarization state of light (PSoL) is:

[0068]

[0069] The angle of linear polarization, AoLP, is either of the following two equations:

[0070]

[0071]

[0072] The degree of linear polarization (DoLP) is:

[0073]

[0074] The experimental measurements of AoLP and DoLP of windshield (WS) are shown in the following table.

[0075]

[0076] In particular, the above results show that AoLP and DoLP can be used to identify the state of the windshield. Once the AoLP and DoLP are known, they can be compared with previous measurements, such as in a lookup table, to determine the state of the windshield.

[0077] Figure 2 The use of photosensor 100 is shown in the case of a clear windshield (diagram 200) and in the case of a windshield with ice on windshield 208 (diagram 202). The depiction of ice on the outside of the windshield is illustrative. Ice or other moisture such as condensation can be on the inside of the window, the outside of the window, or both.

[0078] Diagram 200 shows photosensor 100 pointed toward windshield 208. A distance 210 exists between polarized light source 102 and windshield 208. Above polarized light source 102 is illumination region 206. Windshield 208 is within illumination region 206. Light 206 exits polarized light source 102 and passes through windshield 208. In this case, it forms a light cone 204. In diagram 200, only a minimal amount of light is scattered back toward the set of light detector sensors 104.

[0079] Illustration 202 is very similar, but now there is ice 212 on the outside of the windshield 208. There is now a large amount of scattered light 214 that is returned and received by the set of light detector sensors 104. In this case, there is a cone of light 214 that is scattered back.

[0080] Figure 3 Another example of a vehicle sensor system 300 is shown. It is shown as including a portion 302 of a vehicle. The vehicle includes an instrument panel 304 and a windshield 208. A photosensor 100 is positioned on the instrument panel 304, such that a polarized light source 102 directs an infrared beam 210 toward the windshield 208 at an angle of incidence 306. In this example, ice 212 is present on the exterior of the windshield 208, causing the polarized light 210 to be scattered back as scattered light 214 toward the collection of light detector sensors 104. The placement of ice on the exterior of the windshield in this figure is also illustrative. Alternatively, ice or other condensation may be on the inside of the windshield, on the outside of the windshield, or on both the inside and outside of the windshield.

[0081] Also shown is a so-called black strip or frit strip 308 as part of windshield 208. Frit strip 308 is transparent to infrared light and, for example, does not interfere with the scattering of light 210. In some examples, the photosensor can be positioned so that the illumination area is completely within the frit strip.

[0082] The photosensor 100 is shown as being illustratively connected to a control unit 310. The control unit 310 includes a computing system 312 that communicates with a sensor interface 314. The sensor interface 314 is connected to the photosensor. In some cases, the photosensor may include some computing capabilities and may send sensor data directly to the sensor interface 314. In other cases, the sensor interface 314 may do things like provide power to the polarized light source 102 and also bias the set of light detector sensors 104. In this case, the sensor interface 314 essentially measures the sensor data.

[0083] Computing system 312 is further shown as optionally communicating with a vehicle communication interface 316, which enables computing system 312 to transmit and send messages to other computers within the vehicle. Computing system 312 is further shown as communicating with memory 318. Memory 318 represents various types of memory accessible by computing system 312. In this example, computing system 312 is separate from other controllers or a main controller of the vehicle. In other examples, the functionality of control unit 310 may be integrated into the vehicle's main computer or control system.

[0084] Memory 318 is shown as containing machine-executable instructions 320. Machine-executable instructions 320 enable computing system 312 to perform tasks such as performing numerical calculations and sending and receiving control signals. Memory 318 is also shown as containing sensor data 322 acquired from photosensor 100. This includes measurements from all four of the set of light detector sensors 104. Memory 318 is shown as containing Stokes parameters 324 calculated from sensor data 322. Memory 318 is further shown as optionally containing polarization state 326 of light calculated from Stokes parameters 324. Memory 318 is further shown as containing angle of linear polarization 328 calculated from Stokes parameters 324. Memory 318 is further shown as containing degree of linear polarization 330 calculated from Stokes parameters 324.

[0085] The polarization state 326 (optional), the angle of linear polarization 328, and the degree of linear polarization 330 of the light can be analyzed in different ways. Memory 318 is shown as containing a first option, which is a lookup table 332. Various values can be compared to the lookup table 332 to determine a windshield state signal 338.

[0086] As an alternative to lookup table 332, memory 318 is also shown as containing a neural network 334. Neural network 334 may, for example, contain several fully connected layers and receive as input the polarization state 326 (optionally), the angle of linear polarization 328, and the degree of linear polarization 330 of the light. The output would then be an actual windshield state signal 338, which may, for example, indicate whether the windshield is clean, has ice on it, has thick ice on it, or has condensation on it. Neural network 334 can be trained by acquiring data from windshield 208 in different states and then using it as training data.

[0087] As another alternative, the memory 318 is shown as containing a fuzzy logic module 336 that also takes the three inputs 326 , 328 , 330 and outputs a windshield state signal 338 .

[0088] Once windshield status signal 338 has been determined, it can be communicated to other components or controllers within the vehicle via communication interface 316. In some cases, windshield status signal 338 can be used to control other things, such as the brightness of the HUD, deactivation of the HUD, or activation of a defrost function for vehicle 302.

[0089] Figure 4 A flow chart illustrating a method of operating a vehicle sensor 300 is shown. First, in step 400, sensor data 322 is received from a collection of light detector sensors 104. Next, in step 402, Stokes parameters 324 are calculated based on the sensor data 322. Next, in step 404, the polarization state 326 of the light 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, a windshield status signal 338 is determined by comparing the polarization state 326 (optionally), the angle of linear polarization 328, and the degree of linear polarization 330 of the light to predetermined criteria, such as a lookup table 332 or results from a neural network 334 or a fuzzy logic module 336. Finally, in step 412, the windshield status signal 338 is provided. For example, it can be transmitted to other components of the vehicle using the vehicle communication interface 316.

[0090] Figure 5Another embodiment of the present invention is shown. A head-up display (500) has a housing (510) with a projection output (520). The head-up display (500) emits light through the projection output (520) to project an image having information for the driver or any other passenger of the vehicle onto a windshield, which is not shown in this figure. In the housing (510), a light path from a display (not shown) to an opening is provided using a plurality of reflectors (not shown) to provide a high-quality image. A photoelectric sensor (100) is mounted on the edge of the projection output (520) surrounding the housing (510).

[0091] Figure 6 Another embodiment of the present invention is shown for a black panel head-up display (500). The head-up display (500) is shown in cross-section mounted below an instrument panel (not shown). Figure 6 The windshield (208) in FIG is also shown as a cross-section, wherein the cutting plane of the cross-section is in the plane of the instrument panel and below the surface of the instrument panel. The head-up display has a housing (510) with a projection output (520), wherein the projection output is here established by a display (preferably a TFT display) mounted to the housing (510). The head-up display (500) emits light via the projection output (520) to project an image with information for the driver or any other passenger of the vehicle onto the windshield (208). The photoelectric sensor (100) is mounted side by side to the projection output (520) of the housing (510) and the display of the black panel head-up display (500).

[0092] Reference Signs List

[0093] -- - - - - - - - - - - - - - - - - - - - - - - - -

[0094] 100 photoelectric sensors

[0095] 102 polarized light source

[0096] A collection of 104 light detector sensors

[0097] 106 reference polarization axis

[0098] 108 The first linear polarizer filter at

[0099] 110 A second linear polarizer filter at

[0100] 112 A third linear polarizer filter at

[0101] 114 A fourth linear polarizer filter at

[0102] 200 light rays through the windshield

[0103] 202 Light scattered by ice on the windshield

[0104] Light cone emitted by 204 polarized light source

[0105] 206 lighting areas

[0106] 208 windshield

[0107] 210 Distance between polarized light source and windshield

[0108] 212 Ice on the windshield

[0109] 214 scattered light cone

[0110] 300 vehicle sensor systems

[0111] 302 vehicle part

[0112] 304 Dashboard

[0113] 306 incident angle

[0114] 308 glass strip

[0115] 310 control unit

[0116] 312 Computing Systems

[0117] 314 sensor interface

[0118] 316 vehicle communication interface

[0119] 318 memory

[0120] 320 machine executable instructions

[0121] 322 sensor data

[0122] 324 Stokes parameters

[0123] 326 Polarization State of Light

[0124] 328 linear polarization angle

[0125] 330 degrees of linear polarization

[0126] 332 lookup table

[0127] 334 Neural Network

[0128] 336 Fuzzy Logic Module

[0129] 338 Windshield status signal

[0130] 400 Receive sensor data from a collection of light detector sensors

[0131] 402 Use sensor data to calculate the Stokes parameters describing scattered light

[0132] 404 Optionally calculate the polarization state of the light based on the Stokes parameters

[0133] 406Calculate the linear polarization angle based on the Stokes parameters

[0134] 408Calculate the linear polarization degree based on the Stokes parameters

[0135] 410 Determine a windshield status signal by comparing the polarization state (optionally), the angle of linear polarization, and the degree of linear polarization of the light with predetermined standards

[0136] 420 provides windshield status signal

[0137] 500 head-up display

[0138] 510 head-up display housing

[0139] 520 head-up display projection output

Claims

1. A vehicle sensor system (300), comprising a photoelectric sensor (100), wherein: The photoelectric sensor comprises: a polarized light source (102) configured to illuminate a windshield (208) of a vehicle (302) within an illumination area (206), wherein the illumination area is above the photosensor; - a set of light detector sensors (104) configured to provide sensor data (322) describing scattered light (214) received by the set of light detector sensors from the illumination area; - 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 a set of light detectors, wherein the set of linear polarizer filters comprises filters having respective polarization axes rotated relative to a reference polarization axis (106) 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).

2. The vehicle sensor system according to claim 1, wherein: The vehicle sensor system further includes: - a memory (318) storing machine-executable instructions (320); - a computing system (312), wherein execution of the machine-executable instructions causes the computing system to: - receiving (400) said sensor data from said set of light detector sensors; - using the sensor data to calculate (402) Stokes parameters (324) describing the scattered light; - calculating (404) the polarization state of the light (326), preferably based on said Stokes parameters; - calculating (406) the angle (328) of linear polarization based on the Stokes parameters; - calculating (408) the degree of linear polarization (330) based on said Stokes parameters; - determining (410) a windscreen status signal (338) by comparing the angle of linear polarization and the degree of linear polarization with a predetermined criterion, wherein preferably the polarization state of light is also compared with the predetermined criterion during the determination of the windscreen status signal; and - providing (420) said windshield status signal.

3. The vehicle sensor system according to claim 2, wherein: The windshield status signal is any one of the following: - a condition indicating that ice has been detected on the windshield; - a condition indicating that liquid has been detected on said windscreen; and - Indicates the status of the windscreen if the windscreen is dry.

4. The vehicle sensor system according to claim 3, wherein: If the windshield status is a status indicating that ice is detected on the windshield or a status indicating that liquid is detected on the windshield, the windshield status signal also includes any one of: a brightness change command for the HUD of the windshield, a system deactivation command for the HUD of the windshield, an ice warning, a humidity warning, and a windshield defrost command.

5. A vehicle sensor system according to any one of the preceding claims, wherein: The polarized light source is adapted to provide linearly polarized light for illumination of the illumination area.

6. A vehicle sensor system according to any one of the preceding claims, wherein: The illumination area is 1 cm to 10 cm away from the photosensor, and preferably, the illumination area is 2 cm to 7 cm away from the photosensor.

7. A vehicle sensor system according to any one of the preceding claims, wherein: The polarized light source includes an infrared light source.

8. A vehicle sensor system according to any one of the preceding claims, wherein: The infrared light source is any one of the following: - an infrared light emitting diode and a polarizing filter, and -Solid-state infrared laser.

9. A vehicle sensor system according to any one of the preceding claims, wherein: The vehicle sensor system further includes a vehicle windshield, wherein the vehicle windshield is positioned within the lighting area.

10. The vehicle sensor system according to claim 9, wherein: The polarized light source is configured such that it has an incident angle (306) with the windshield between 15 degrees and 75 degrees.

11. The vehicle sensor system according to claim 9 or 10, wherein: The vehicle sensor system further comprises a head-up display (500) having a housing (510), wherein the head-up display (500) comprises the photoelectric sensor (100) or a portion thereof.

12. The vehicle sensor system according to claim 11, wherein: At least the set of light detector sensors (104) is located inside or outside the housing (510) of the head-up display (500).

13. The vehicle sensor system according to 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 the light source is the polarized light source (102) of the photosensor (100).

14. The vehicle sensor system according to any one of 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 photosensor (100) is positioned side-by-side with respect to the projected output (520) of the head-up display (500).

15. The vehicle sensor system according to claim 9 or 10, wherein: The vehicle windshield includes a ribbon of glass (308), wherein the photosensor is positioned such that the illumination area is within the ribbon of glass.

16. The vehicle sensor system according to any one of claims 9, 10 or 11, wherein: The vehicle includes an instrument panel (304), wherein the photosensor is at least partially mounted within the instrument panel.

17. A vehicle (302) comprising a windshield and a vehicle sensor system according to any one of the preceding claims.

18. A method of operating a vehicle sensor system (300) comprising a photoelectric sensor (100), wherein the photoelectric sensor comprises: a polarized light source (102) configured to illuminate a windshield (208) of a vehicle (302) within an illumination area (206), wherein the illumination area is above the photosensor; - a set of light detector sensors (104) configured to provide sensor data (322) describing scattered light (214) received by the set of light detector sensors from the illumination area; - a set of linear polarizer filters (108, 110, 112, 114), each filter configured to filter the scattered light before it reaches a corresponding one of the set of light 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); The method comprises: - receiving (400) said sensor data from said set of light detector sensors; - using the sensor data to calculate (402) Stokes parameters (324) describing the scattered light; - preferably, calculating (404) the polarization state of the light (326) based on said Stokes parameters; - calculating (406) the angle (328) of linear polarization based on the Stokes parameters; - calculating (408) the degree of linear polarization (330) based on said Stokes parameters; - determining (410) a windscreen status signal (338) by comparing the angle of linear polarization and the degree of linear polarization with a predetermined criterion, wherein, preferably, the polarization state of light is also compared with the predetermined criterion during the determination of the windscreen status signal; and - providing (420) said windshield status signal.

19. A computer program comprising machine-executable instructions (320) for execution by a computing system (312), the computing system (312) being configured to control a vehicle sensor system (300), wherein the vehicle sensor system comprises a photoelectric sensor (100), wherein the photoelectric sensor comprises: a polarized light source (102) configured to illuminate a windshield (208) of a vehicle (302) within an illumination area (206), wherein the illumination area is above the photosensor; - a set of light detector sensors (104) configured to provide sensor data (322) describing scattered light (214) received by the set of light detector sensors from the illumination area; and - a set of linear polarizer filters (108, 110, 112, 114), each filter configured for filtering the scattered light before it reaches a respective one of a set of light detectors, wherein the set of linear polarizer filters includes filters having respective polarization axes rotated relative to a reference polarization axis (106) 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); wherein execution of the machine-executable instructions causes the computing system to: - receiving (400) said sensor data from said set of light detector sensors; - using the sensor data to calculate (402) Stokes parameters (324) describing the scattered light; - calculating (404) the polarization state of the light (326), preferably based on said Stokes parameters; - calculating (406) the angle (328) of linear polarization based on the Stokes parameters; - calculating (408) the degree of linear polarization (330) based on said Stokes parameters; - determining (410) a windscreen status signal (338) by comparing the angle of linear polarization and the degree of linear polarization with a predetermined criterion, wherein the polarization state of light is preferably also compared with the predetermined criterion during the determination of the windscreen status signal; and - providing (412) said windshield status signal.

20. A head-up display (500) comprising the vehicle sensor system according to any one of claims 1 to 8.

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