GB2536238A

GB2536238A - Windshield monitoring system

Info

Publication number: GB2536238A
Application number: GB1503984.5A
Authority: GB
Inventors: Beloe Neil; Parsons Jonathan
Original assignee: Jaguar Land Rover Ltd
Current assignee: Jaguar Land Rover Ltd
Priority date: 2015-03-09
Filing date: 2015-03-09
Publication date: 2016-09-14
Anticipated expiration: 2035-03-09
Also published as: GB201503984D0; GB2536238B

Abstract

The present invention relates to a windshield monitoring system. The system comprises a laminated windshield 14 having an infrared reflective (IRR) layer 18. The system also comprises an infrared light source arranged to direct a beam of light 32 into the windshield 14 at an incidence angle θi arranged to subject the beam of light 32 to total internal reflection at a windshield to air interface to propagate the beam of light across the windshield 14 towards an opposing edge thereof, and arranged to refract light away from the windshield 14 at a windshield to contaminant interface. The infrared light 32 is also arranged to reflect off the infrared reflective layer 18. The system also comprises an infrared light detector 34 arranged to detect that the light beam has been refracted 38 away from the windshield 14.

Description

WINDSHIELD MONITORING SYSTEM

TECHNICAL FIELD

The present disclosure relates to a windshield monitoring system particularly, but not exclusively, for a vehicle. Aspects of the invention are directed to a windshield monitoring system, a windshield clearing system, a vehicle including the same, a method of monitoring a windshield, and a method of clearing a windshield.

BACKGROUND

A vehicle such as a car or the like includes a frame supporting several windshields. A windshield is a term of art covering a front windscreen, a rear windscreen, or a side window, of which there are several. A windshield may comprise a laminate construction or it may be a singular piece of glass. A windshield serves several functions including segregating interior and exterior environments of the vehicle whilst providing visible communication between the two.

Under ideal conditions, interior and exterior surfaces of the windshield are characterised by a glass to air interface. In practice, various sources of contamination can build up on either surface affecting the visibility for the vehicle occupants. Water based contamination such as ice or condensation can be eradicated by heating the windshield.

One way in which the windshield can be heated is by using hot air blowers. Air blowers can be oriented by a driver or other occupant to direct a stream of air on the windshield. In addition, heating elements can be embedded in to the windshield itself. Such a heating element usually includes a series of parallel wires which heat up due to electrical resistance when an electrical current is passed across them. Like the air blowers, these electrically conducting wires can be activated manually by a driver or other vehicle occupant pressing a push button on the vehicle instrument panel.

Such manually operated heating elements are inherently inefficient. This is because a driver must actively detect the contamination and activate the heating element accordingly. Typically, a driver would not bother to activate the heating elements unless the source of contamination was affecting their visibility at which point the area of contamination could be relatively large. In addition, a driver will always over compensate with regards to clearing time by leaving the blowers or heating elements on longer than necessary.

Various attempts have been made to provide automatic contamination detection systems. One such system uses an infrared light detector within the vehicle interior in an attempt to detect any rain water on the exterior surface of the windshield by monitoring for reflection of the infrared light resulting from the light passing through the rain drops. Such systems are not very popular. Primarily, this is due to the fact that it is desirable to include an infrared reflective (IRR) layer as part of the laminated windshield to reflect away heat energy from the vehicle cabin. IRR glass has an internal conductive metallic layer which is reflective to infrared light. Accordingly, the infrared light for the rain sensor cannot pass the wind shield to detect the presence of rain water. In order to make the system usable, a window has to be cut in to the IRR layer by laser cutting. The rain detection system is thus limited to the size of the window cut in to the glass. This is a common trait with rain detection systems, which are generally limited to detecting rain in a small area of the windshield. Cutting the window in to the IRR layer removes any of the benefits associated with using!RR glass, though in practice the affected area is relatively small. In addition, such a laser cutting process is expensive.

Other forms of windshield contaminant detection systems are also known. For instance, a dew point detection system is known for detecting dew formation on an interior surface of a windshield. Such dew point detection systems work by estimating dew formation by calculation based on humidity and temperature. Since these dew point detection systems are based on calculation rather than being detected directly, they are inherently inaccurate. As a result, any windshield clearing mechanisms, such as heating mechanisms, used to clear the windshield based on the detection of dew in this way may be activated in an untimely manner. Untimely activation of the clearing mechanisms wastes energy since the windshield may either be heated when no dew is present or be activated later than required allowing a relatively large area of dew to form, which would be harder to clear.

It is an aim of the present invention to further improve on the prior art.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a windshield monitoring system. The system may comprise a laminated windshield having an infrared reflective (IRR) layer. The system may comprise an infrared light source arranged to direct a beam of light into the windshield at an incidence angle arranged to subject the beam of light to total internal reflection at a windshield to air interface to propagate the beam of light across the windshield towards an opposing edge thereof. The angle of incidence may be arranged to refract light away from the windshield at a windshield to contaminant interface, wherein the infrared light is arranged to reflect off the infrared reflective layer. The system may comprise an infrared light detector arranged to detect that light has been refracted away from the windshield.

The windshield monitoring system according to embodiments may allow for contamination to be detected before it obscures a relatively large area of the windshield which saves energy in removing the contamination by heating the glass. It is counterintuitive to use infrared light for detecting contamination of a windshield surface since the windshield has the infrared reflective layer not allowing the infrared light to pass. However, in this case, the infrared reflective layer is used to benefit the propagation of the infrared light beam across the windshield.

The light detector may be arranged to monitor intensity of the internally reflected light to detect refracted light by a drop in light intensity.

The light source may be arranged to direct the beam of light on an interior side of the infrared reflective layer, and/or wherein the light source may be arranged to direct the beam of light on an exterior side of the infrared reflective layer.

A beam of light directed on the interior side of the infrared reflective layer means the contamination on the interior surface of the wind shield can be detected. In a similar way, a light beam directed on the exterior side of the infrared reflective layer will detect surface contamination on the exterior side of the wind shield.

The light detector may comprise a photodiode.

The light source may comprise a plurality of light emitters forming an array substantially spanning along an edge of the windshield and wherein each emitter may be arranged to direct a beam of infrared light across the windshield towards an opposing edge thereof.

The array of light emitters substantially spanning along an edge of the windshield provides for a wide area of coverage for the detection system.

The windshield monitoring system may comprise a locating module arranged to locate the contamination based on which light detector has detected the contamination.

The locating module provides for more accurate contamination detection which in turn allows for a more energy efficient system since the area affected by the contamination can be targeted for clearing before the contamination spreads.

The light source may comprise two mutually orthogonal arrays of emitters wherein each array may substantially span along adjacent edges of the windshield and may be arranged to direct light to a respective opposing edge thereof.

The two mutually orthogonal arrays provides for two dimensional positioning of any detected contamination such that the contamination can be assigned a coordinate on the windshield.

The light detector may comprise a plurality of light detectors each being associated with a different light emitter.

The system may comprise a noise filter to distinguish light emitted from the light source from other detected light.

Reducing the detection of other detected light reduces the risk of erroneous readings when detecting the presence of refracted light since light can be detected from sources other than the emitters of the windshield monitoring system.

The noise filter may comprise a lock-in amplifier.

A lock-in amplifier is a reliable component which lends itself particularly well to this application.

The system may comprise a pulsar arranged to pulsate the light according to a predefined pattern.

Pulsating the light makes it easier to detect the source of the detected light since light coming from other sources would not be pulsated in the same way.

Each light beam may be pulsed, strobed, or shuttered according to a unique pattern or may be phase shifted relative to the other light beam.

A unique pattern per light emitter or phase shifted light relative to the other emitters is easier to identify the source of the light which can further aid in locating the contamination on the wind shield.

The windshield may be a front windscreen, a rear windscreen, or a side window.

The front and rear windscreens would benefit particularly well from this windshield monitoring system since it is these windshields which have the biggest impact on driver visibility. Side windows, particularly front side windows also have an effect on driver visibility.

The contamination may be selected from the list of moisture, ice, liquid water.

These contaminants are particularly suited to this application since they are most easily treated with other ancillary systems of the vehicle such as heaters and/or air blowers.

Treatment is more difficult for other contaminants, for example, dirt.

The angle of incidence of the light beam may be between about 43° and about 65°.

The critical angle for a glass to air interface is about 43° and the critical angle for a glass to water interface is about 65° due to the difference in refractive index of air and water.

Accordingly, an angle of incidence of the light in this range would be reliable enough to refract away light only at a glass to water interface but not at a glass to air interface.

According to a further aspect of the present invention there is provided a windshield clearing system comprising the aforementioned windshield monitoring system; a windshield clearing system; and a control module arranged to control the windshield clearing system to clear the windshield in response to detecting refracted light.

The windshield clearing system may comprise a heating mechanism.

The heating mechanism may be divided into a plurality of heating elements and wherein the control module may be arranged to control the heating element to heat the windshield at a corresponding location as the detected contamination.

Dividing the heating element into a plurality of heating elements, or zones, and only heating the heating element corresponding to the location of detected contamination reduces the energy consumption by the vehicle since no energy is wasted clearing uncontaminated areas.

The heating element may comprise a resistance heating element.

The resistance heating element may comprise a metallic layer.

A metallic layer is easy to deposit on to a windshield at relatively low cost.

The windshield clearing system may comprise a blower control unit for electrical communication with an air blower arranged to selectively direct air towards the windshield.

Alternatively, the windshield clearing system may comprise a wiper system.

The windshield clearing system may include a termination module to stop operation of the clearing system in response to contamination no longer being detected. Terminating clearing leads to further energy efficiencies since attempting to clear an already clear windshield is just wasted energy. This is particularly important for electric vehicles and hybrid electric vehicles.

Alternatively or in addition, the termination module may be arranged to stop operation of the clearing system after a predetermined time period. This is important for false triggers resulting from, for instance, windshield cracks since the clearing system would not be able to 'clear' the crack and so allowing the system to continue attempting to clear the crack would waste energy.

The control module may be arranged to emit an indication after a predefined number of times of stopping operation of the clearing system, in the case of stopping after a predetermined time period. The indication can be used off-line, for instance during manufacture, or on the vehicle as a dashboard indication or a signal available during a maintenance inspection, to indicate that the windshield requires inspection since such reoccurrences may be due to the presence of windshield cracks, which cracks are not clearable by the clearing system.

According to a further aspect of the present invention there is provided a vehicle comprising the aforementioned windshield clearing system.

According to a further aspect of the present invention there is provided a method of detecting surface contamination on a windshield having an infrared reflective (IRR) layer. The method may comprise emitting an infrared light beam into an edge the windshield at an angle of incidence arranged to subject the light beam to total internal reflection at a windshield to air interface to propagate the light beam towards an opposing edge of the windshield. The angle of incidence may be arranged to refract the beam of light away from the windshield at a windshield to contaminant interface. The method may comprise reflecting the light off the IRR layer. The method may comprise detecting surface contamination by monitoring light from the beam of light being refracted away from the windshield.

The method may comprise monitoring light reflected internally within the windshield. The method may comprise determining the presence of surface contamination by a drop in light intensity due to light being refracted away from the windshield.

The method may comprise filtering out noise from other detected light not associated with the emitted light.

The method may comprise pulsating the light beam according to a predefined pattern.

The method may comprise emitting a plurality of light beams substantially spanning along an edge of the windshield. The method may comprise detecting any refracted light from each of the light beams. The method may comprise associating the location of the refracted light with one of the light beams to determine the location of the contamination.

The method may comprise; emitting the plurality of light beams as two arrays, each array substantially spanning along adjacent edges of the windshield. These adjacent edges may be arranged orthogonally to one another.

The method may comprise emitting an infrared light beam across an interior side of the IRR layer of the windshield. The method may comprise emitting an infrared light beam across an exterior side of the IRR layer of the windshield.

According to a further aspect of the present invention there is provided a method of clearing a windshield having an infrared reflective (IRR) layer comprising; detecting the presence of surface contamination using the aforementioned method; and heating the windshield in response to detecting refracted light.

Heating the windshield may include dividing the windshield into a plurality of zones and heating a zone corresponding to an area of the windshield where contamination has been detected.

Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible. The applicant reserves the right to change any originally filed claim or file any new claim accordingly, including the right to amend any originally filed claim to depend from and/or incorporate any feature of any other claim although not originally claimed in that manner.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 shows part of a windshield monitoring system according to an aspect of the present invention; Figure 2 shows a block diagram of windshield monitoring system from Figure 1; Figure 3 shows a windshield clearing system according to another aspect of the present invention; Figure 4 shows a section view of the windshield monitoring system from Figure 1, in operation not detecting contamination; Figure 5 shows a similar view to Figure 4 of the windshield monitoring system detecting contamination; and Figure 6 shows a similar view to Figure 3 according to an alternative embodiment of an embodiment of the present invention.

DETAILED DESCRIPTION

With reference to Figure 1, a vehicle 10 includes a frame 12 supporting a plurality of windshields 14 (one shown). The term windshield 14 includes a front windscreen, or a rear windscreen, or a side window, of which there are several. Each windshield 14 either comprises a plurality of sheets of laminated glass or a singular sheet of glass.

With brief reference to Figure 4, a laminated windshield 14 includes a plurality of sheets.

Said sheets include outer and inner sheets of glass 16, 17, an infrared reflective (IRR) film 18, and an intermediate layer 19. The intermediate layer 19 is made from Polyvinyl Butyral (PVB). PVB is selected because it has the same refractive index as the inner 16 and outer 17 sheets of glass. The windshield 14 separates an exterior environment 20 from an interior environment 22. Accordingly, the windshield 14 has an exterior surface 24 and an interior surface 26.

With reference to Figures 1 and 2, the vehicle 10 also includes a windshield monitoring system, part of which is shown in Figure 1 with a more detailed version in the form of a block diagram being provided in Figure 2.

With specific reference to Figure 1, the windshield monitoring system includes a light source in the form of a plurality of light emitters 30. The light emitters are Light Emitting Diodes (LEDs). The light emitters are configured to emit beams 32 of infrared light. The beams 32 are narrow beams of light. The emitters 30 are provided as two arrays of emitters. The arrays of emitters are arranged along adjacent, mutually orthogonal edges of the windshield 14. In particular, one array is provided along a right hand side edge of the windshield 14. The other array is provided along a lower horizontal edge of the windshield 14. The two arrays of light emitters 30 are thus mutually orthogonal. Each emitter 30 is arranged to direct a beam of infrared light 32 in to the windshield 14 at an angle of incidence, relative to a normal line of incidence N between about 42° and about 65°. The reasons for this are provided in more detail below. The light emitters 30 span along each respective edge of the windshield 14. Beams of light 32 from the same array are substantially parallel to one another. In this way, almost complete coverage of the windshield can be provided by the two mutually orthogonal arrays of light emitters 30. Each emitter 30 is encapsulated in a refractive index matched medium along the edge of the windshield.

The windshield monitoring system also includes a plurality of light detectors 34. Each light detector is a photodiode. The light detectors 34 are also provided as two mutually orthogonal arrays. The two arrays of light detectors 34 are provided along a left side edge of the windshield 14 and a top edge of the windshield 14 respectively. Each light detector 34 is associated with a unique light emitter 30 such that there are equal numbers of light detectors and emitters. The light detectors 34 have the same separation distance as the light emitters 30. As will be described in more detail below, the light detectors 34 are arranged to detect the intensity of light reflected internally within the windshield 14 from the corresponding emitter 30 at the opposing edge of the windshield 14.

As will be described in more detail below, any contamination 36 on the windshield may result in a light beam 32 being refracted away from the windshield 14. Refracted light 38 causes a drop in intensity of the internally reflected light 32 detected by the light detector 34.

With specific reference to Figure 2, the windshield monitoring system includes a noise filter 39 to distinguish light emitted from the light source from other detected light. The noise filter comprises a pulsar 40 and a lock-in amplifier 42.

The pulsar 40 includes a motor 44 and a rotatable disc 46. The motor 42 is arranged to rotate the disc about a rotation axis (not shown) at a variable speed measure in revolutions per minute (RPM). The disc includes successive transparent 48 and opaque 50 regions. A light beam 32 emitted from the light emitter 30 is directed in to the disc 46. The light beam 32 impinges on the successive transparent 48 and opaque 50 regions since the axis of rotation of the disc 46 is misaligned with the light beam 32. The light beam 32 is allowed to pass through the transparent regions 48 but is blocked by the opaque regions 50. By opaque, it is meant that any material can be used which blocks out infrared light. The transparent 48 and opaque 50 regions are not consistent in area so as to vary the duration of light passing the disc 46. In this way, the pulsar 40 is arranged to pulsate the light according to a predefined pattern corresponding the sizes of the transparent 48 and opaque 50 regions and the speed at which the motor 44 drives the disc 46.

The disc 46 and/or the speed of the motor 44 are varied across the array of light emitters 30 such that each light beam 32 is pulsated according to a unique pattern. In this way, light can be identified as a originating from a specific light emitter 30. Another way in which this can be achieved is to phase shift light from each of the light emitters 30 relative to the other light emitters 30.

The lock-in amplifier 42 is connected to the motor 44 to monitor the RPM thereof. The lock-in amplifier 42 also includes a data store for storing the geometric profiles of the rotatable discs 46. The lock in amplifier can compare the received light with that calculated as being an expected pattern of light such that the light beam 32 originating from the light emitter 30 can be distinguished from other light 52 originating from a variety of other sources.

As an alternative, the pulsar may use strobing effects or shuttering to pulsate the light beam rather than using the disc 46 as described above.

The windshield monitoring system also includes a locating module 54 which is linked to the light detectors 34. Any light detected by a specific light detector 34 can be used to locate the position of the contamination as a two dimensional coordinate by identifying which detector 34 in each array has detected the refracted light.

With reference to Figure 3 the vehicle 10 also includes a windshield clearing system 60. The windshield clearing system 60 includes the windshield monitoring system, a control module 62, and a clearing element, in this embodiment in the form of a heating mechanism 64.

The control module 62 is provided as electronic data on a non-volatile memory component of an on board computer system. The computer system also includes a processor to execute the electronic data to operate the control module 62. The locating module 54 is also provided in the same way, namely, electronic data stored on the non-volatile memory component of the on board computer. The control module 62 is arranged to apply a voltage across the heating mechanism 64 in response to a demand to heat the heating element to clear the contamination.

The control module 62 includes a termination module 63 as part of the electronic data stored on the memory component of the on-board computer. The termination module 63 is arranged to send a termination command to the heating mechanism 64 to terminate heating in response to the detectors 34 (Figure 2) ceasing to detect refracted light 38.

The heating mechanism 64 is divided in to a plurality of zones, or heating elements. The zones are divided in to active heating elements 66 and passive heating elements 68. Active heating elements 66 are defined as those that can be heated and are provided with electrically conductive layers. These passive zones 68 are very small in dimension so as to prevent a pattern of unclear glass during operation. These passive zones 68 are considered as boundaries to the active zones 66. The control module 62 can apply a voltage across the metallic layer of any of the active heating elements 66. The corresponding electrical current heats a zone of the windshield corresponding to the location of the detected contamination.

The heating mechanism 64 comprises a resistant heating element which is a metallic layer.

The metallic layer is vapour deposited on to the windshield 14. The metallic layer is silver alloy. However, other electrically conductive materials would suffice, for instance some organic materials like graphene, or even the IRR layer itself.

With reference to Figure 4, in operation, the light emitter 30 emits a beam of infrared light 32 in to an edge of the windshield 14 such that the angle of incidence of the light on the glass to air interface is between about 42° and about 65°. These angles are measured relative to a normal angle of incidence N relative to the interior and exterior surfaces 26 and 24 of the windshield 14.

The critical angle, 0,, for a glass to air interface is about 42°. The critical angle, 0,, for a glass to water interface is about 65°. The difference in critical angle is due to the difference in refractive index between air and water. Any light below an angle of incidence, el, lower than a critical angle, 8,, would refract away from the glass. Any angle of incidence, el, above the critical angle, 9,, would reflect internally within the glass. This phenomenon is total internal reflection.

This windshield clearing system is most suitable for use in clearing water based contamination such as moisture (in the form of fogging or misting of the windshield), ice, and liquid water since water evaporates relatively easily through heat. Accordingly, an angle of incidence, e, of a beam of light 32 between about 43° and about 65° would reflect internally at a glass to air interface and refract away from the glass at a glass to contaminant interface.

The light detector 34 constantly monitors the intensity of light reflected internally across the windshield 14. Since the light beam 32 is infrared light, the light naturally reflects off the IRR layer 18 inside the laminated windshield 14. In this way, a light beam 32 can be directed on an interior side of the IRR layer 18. Additionally, or alternatively, the light beam 32 can be directed on an exterior side of the IRR layer 18. This can be achieved by directing adjacent emitters 30 to direct their beam of light 32 on opposite sides of the reflective IRR layer 18. Alternatively, a pivoting mechanism can be used to pivot an emitter 30 such that one pulse of light 32 can be directed on the interior side of the IRR layer 18 and a subsequent pulse of light 32 from the same emitter can be directed to an exterior side of the IRR layer 18.

With reference to Figure 5, any contamination 36 changes the critical angle, BC, at the interface as described above. When the light beam 32 impinges on a glass to contaminant interface, light is refracted away from the windshield 14 as refracted light 38. The refracted light 38 results in a reduction in intensity of the internally reflected light beam 32. The detector 34 detects this reduction in intensity of light. A drop in intensity of light monitored by the light detector 34 is attributable to the presence of contamination 36 on the windshield 14.

The noise filter 39 filters out any light detected by the detector 34 attributable to other sources than the light source 30. The locating module 54 provides a two dimensional coordinate of the contamination 36 based on which of the detectors 34 have detected the contamination. This coordinate will distinguish between the interior and the exterior of the windshield 14 using the same approach since each emitter 30 can be configured to direct light either down and interior or exterior side of the IRR only. Using this coordinate, the control module 62 passes a voltage to one of the active heating zones 66 corresponding to the location where contamination has been detected.

When the detectors 34 experience an intensity of the received light returning to expected levels, the control module 62 determines that contamination 36 has cleared. The termination module 63 reduces the voltage across the heating element 64 to zero Volts. Temperature of the heating element 64 reduces accordingly.

There are various energy efficiencies in using this system since heating the windshield 14 has been made automatic in response to detecting any contamination 36 rather than letting the contamination 36 propagate to a point which might affect the driver's visibility. In addition, heating only an area of the windshield 14 corresponding to the location of contamination 36 is more energy efficient compared to a case where the entire windshield 14 is heated even when contamination 36 is localised.

Various alternative embodiments are also possible within the scope of the appended claims.

One such alternative embodiment will now be described. Those features in common with the previous embodiment are labelled with like reference numerals.

In this alternative embodiment, the windshield monitoring system is the same as the previously described embodiment and so is not described in any further details here.

With reference to Figure 6, the windshield clearing system 160 of the alternative embodiment includes the control module 62 having a termination module 63 installed therewith. The windshield clearing system also includes a windshield wiper system 164. The windshield wiper system 164 includes a motor 166 powering a wiper blade 168.

There are two wiper arms 168 shown in Figure 6 however this may be reduced depending on the windshield incorporating the windshield clearing system 160. The wiper arms 168 are of conventional design incorporating being coupled to the motor 166 in a known manner. The wiper arms 168 each support a wiper blade. The wiper blade is made from rubber and is arranged to contact the exterior surface of the windshield 14.

There are two motors 166 shown in Figure 6, each for powering a wiper arm 168. However, other configurations may be employed such as a single motor 166 driving a common linkage attached to both wiper arms 168. The motor 166 is arranged to rotate the wipers arm 168 back and forth over the exterior surface of the windshield 14 in a rotary fashion. The motor 166 can be configured to operate at several speeds.

In one mode of operation, when the windshield monitoring system (Figure 5) detects exterior surface contamination on the windshield 14, the control module 62 (Figure 6) configures the motors 166 to rotate the wiper arms 168 over the windshield. The wiper blades clear the windshield 14 by wiping away water. Once the windshield monitoring system (Figure 5) ceases to detect the presence of water on the windshield 14, the termination module 63 (Figure 6) commands the motors to terminate stop, after a cycle has been completed.

In another mode of operation, when the locating module 54 (Figure 2) has detected localised contamination, the controller 62 (Figure 6) will configure the motors 166 to move the wiper arms 168 to the area where contamination has been detected. Next, the motor 166 will move the wiper arm 168 back and forth over the contamination. Again, wiping will terminate once the windshield monitoring system ceases to detect contamination.

This alternative windshield clearing system has been described with reference to water based contamination. However, other contaminants such as dirt can be cleared in this way too by wiping away the dirt using the wiper blades. The wiper cycle can be a wash/wipe cycle if the contamination remains after an acceptable period of time. That said, some contaminants such as windshield cracks may cause false triggers. In this case, the termination module 63 over-rides the control module 62 after a pre-determined time period to save energy. If a predefined number of false triggers occur then the control module 62 is arranged to emit an indication to have the windshield 14 checked. The indication can be used on the vehicle 10 or off-line during manufacture or maintenance inspection. Doing so will allow the windshield to be checked since such reoccurrences may be due to cracks in the windshield 14. If the windshield 14 is found to cracked, then the windshield 14 can be replaced.

It will be appreciated that in addition, or as an alternative to clearing the interior of the windshield 14 using electrically conductive heating elements, the windshield clearing system may be arranged to generate a control signal for communication to a vehicle based heating ventilation and air conditioning (HVAC) unit comprising an air blower. The HVAC unit is arranged to condition the air in the vehicle cabin. When contamination of the interior surface of the windshield is detected, the windshield clearing system generates a signal indicative of the location and severity of detected water based contamination on the interior surface of the windshield. In response to this signal, a fan or blower located in the vehicle HVAC unit may be activated, directing moving air across the interior surface of the windshield to accelerate clearing. Depending on detected ambient conditions, such as cabin air temperature and humidity and outside air temperature and humidity, the HVAC unit blower may be used in addition to the heating elements located on the windshield 14. In this way, the termination module 63, as described above, may also have the authority to terminate an action of the HVAC unit that had been previously requested in response to a detected water based contamination on the windshield.

Claims

CLAIMS1. A system comprising: a laminated windshield having an infrared reflective (IRR) layer; an infrared light source arranged to direct a beam of light into the windshield at an incidence angle arranged to subject the beam of light to total internal reflection at a windshield to air interface to propagate the beam of light across the windshield towards an opposing edge thereof, the angle of incidence arranged to refract light away from the windshield at a windshield to contaminant interface, wherein the infrared light is arranged to reflect off the infrared reflective layer; and an infrared light detector arranged to detect that light has been refracted away from the windshield.
2. The system of Claim 1 wherein the light detector is arranged to monitor intensity of the internally reflected light to detect refracted light by a drop in light intensity.
3. The system of Claim 1 or Claim 2 wherein the light source is arranged to direct the beam of light on an interior side of the infrared reflective layer, and/or wherein the light source is arranged to direct the beam of light on an exterior side of the infrared reflective layer.
4. The system of any preceding claim wherein the light detector comprises a photodiode.
5. The system of any preceding claim wherein the light source comprises a plurality of light emitters forming an array substantially spanning along an edge of the windshield and wherein each emitter is arranged to direct a beam of infrared light across the windshield towards an opposing edge thereof.
6. The system of Claim 5 wherein the windshield monitoring system comprises a locating module arranged to locate the contamination based on which light detector has detected the contamination.
7. The system of Claim 5 or Claim 6 wherein the light source comprises two mutually orthogonal arrays of emitters wherein each array substantially spans along adjacent edges of the windshield and arranged to direct light to a respective opposing edge thereof.
8. The system of any of Claims 5 to 7 wherein the light detector comprises a plurality of light detectors each being associated with a different light emitter.
9. The system of any preceding claim comprising a noise filter to distinguish light emitted from the light source from other detected light.
10. The system of Claim 9 wherein the noise filter comprises a lock-in amplifier.
11. The system of any preceding claim comprising a pulsar arranged to pulsate the light according to a predefined pattern.
12. The system of Claim 11 and Claim 7, wherein each light is pulsed according to a unique pattern or is phase shifted relative to the other light emitters.
13. The system of any preceding claim wherein the windshield is a front windscreen, a rear windscreen, or a side window.
14. The system of any preceding claim wherein the contamination is selected from the list of moisture, ice, liquid water.
15. The system of any preceding claim wherein the angle of incidence of the light beam is between about 43° and about 65°.
16. A windshield clearing system comprising a windshield monitoring system of any preceding claim; a windshield clearing element; and a control module arranged to control the windshield clearing element to clear the contamination in response to detecting refracted light.
17. The windshield clearing system of Claim 16 wherein the windshield clearing element comprises a heating mechanism.
18. The system of Claim 17 wherein the windshield monitoring system is according to Claim 6, and wherein the heating mechanism is divided into a plurality of heating elements and wherein the control module is arranged to control the heating elements to heat the windshield at a location corresponding to the detected contamination.
19. The system of Claim 17 or Claim 18 wherein the heating element comprises a resistance heating element.
20. The system of Claim 19 wherein the resistance heating element comprises a metallic layer.
21. The system of Claim 16 wherein the windshield clearing element comprises a windshield wiper system.
22. The system of Claim 21 wherein the windshield wiper system is arranged to cycle selectively over an area of the windshield where exterior contamination has been detected.
23. The system of any of Claims 17 to 22 comprising a termination module to stop operation of the clearing system in response to contamination no longer being detected.
24. The system of any of Claims 17 to 22 wherein the termination module is arranged to stop operation of the clearing system after a predetermined time period.
25. The system of Claim 24 wherein the controller is arranged to emit a warning in response to stopping operation of the clearing system after more than a predefined number of times.
26. A vehicle comprising the windshield clearing system of any of Claims 16 to 25.
27. A method of detecting surface contamination on a windshield having an infrared reflective (IRR) layer, the method comprising; emitting an infrared light beam into an edge the windshield at an angle of incidence arranged to subject the light beam to total internal reflection at a windshield to air interface to propagate the light beam towards an opposing edge of the windshield, and the angle of incidence arranged to refract the beam of light away from the windshield at a windshield to contaminant interface; reflecting the light off the IRR layer; and detecting surface contamination by monitoring light from the beam of light being refracted away from the windshield.
28. A method of clearing a windshield having an infrared reflective (IRR) layer comprising; detecting the presence of surface contamination using Claims 27; and using a windshield clearing system, clearing the windshield in response to detecting refracted light.
29. A windshield monitoring system, a windshield clearing system, a vehicle, a method of detecting surface contamination on a windshield, and a method of clearing a windshield as substantially described herein with reference to the accompanying figures.