GB2536237A

GB2536237A - Windshield monitoring system

Info

Publication number: GB2536237A
Application number: GB1503981.1A
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: GB201503981D0; GB2536237B

Abstract

The present invention relates to a windshield monitoring system, comprising; a windshield 104 for a vehicle 100; a plurality of light emitters 108 forming an array, each emitter 108 arranged to direct a beam of light into an edge of the windshield 104 at an angle of incidence 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 to an opposing edge thereof, and the angle of incidence being arranged to refract the light beam away from the windshield at a windshield to contaminant interface; the system comprising a light detector arranged to detect that light from the beam of light has been refracted away from the windshield; and wherein the emitters 108 are separated substantially across a length of the windshield 104.

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 relate 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, or 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.

Windshields are prone to having their surfaces contaminated which can result in a degradation of visibility. Water based contaminants are most frequent and result from differences in humidity and temperature between interior and exterior environments of the vehicle. For instance, on a very cold day, moisture from occupants respiration and/or wet clothing can condense on an interior surface of a windshield. Such condensation can be problematic from a visibility perspective when condensation covers large areas of a windshield. Another example of problematic windshield contamination is ice on an external surface of the windshield on a particularly cold day.

Typically, vehicles are provided with heating provisions which can be operated to clear such contamination. One such heating provision includes air blowers which can be manually oriented by a vehicle occupant towards the interior surface of the windshield.

Another heating provision includes a series of electroconductive parallel wires embedded into the laminated glass. The wires heat the glass by an energy transfer from electrical energy to thermal energy. Such a system can be operated manually by an occupant pressing a push button on an instrument panel. However, using such a manually operated system requires an occupant to monitor the windshield themselves. At the time of detection of any contamination, the area of contamination is likely to be large resulting in excessive power being required to clear the contamination. In addition, the user will inevitably always over compensate and leave the heating element on for much longer than is required. Accordingly, energy operating the heating element will be wasted unnecessarily.

Attempts have been made to detect the present of contamination automatically.

With reference to Figures 1 A and 1 B, one known system includes a windshield 10 having a combined emitter/detector 12 mounted on a reverse (non-reflective) side of a rear-view mirror 14. The emitter shines infrared light 18 onto an interior surface 16 of the windshield 10. Since the windshield 10 is oriented at an acute angle of inclination relative to the rear-view mirror, any reflected light 20 from the emitter reflects away from the detector 12.

However, the presence of contamination 22 in the area of the windshield 10 where the light 18 is shone is scattered on reflection. The scattered light 20a is likely to impinge on the detector 12. Any detected light is determined to be attributable to the present of surface contamination 22.

Such a system is not ideal since the scattered light 20a may not impinge on the detector 12 and in addition only contamination in the area of the windshield 10 where light is shone can be detected. Accordingly, such attempts to automatically heat the windshield to clear the contamination are not energy efficient since it is likely that large areas of contamination can develop before being detected. In addition, the entire windshield may be heated if a small amount of condensation develops in the region of the sensor.

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 comprising a windshield for a vehicle. The system may comprise a plurality of light emitters forming an array. Each emitter may be arranged to direct a beam of light into an edge of the windshield at an angle of incidence 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 to an opposing edge thereof. The angle of incidence may be arranged to refract the light beam away from the windshield at a windshield to contaminant interface The system may comprise a light detector arranged to detect that light from the beam of light has been refracted away from the windshield. The emitters may be separated substantially across a length of the windshield.

Contamination is defined as any impurities at a windshield surface resulting in an interface which could alter visibility through the windshield. Using total internal reflection and refraction of light beams provides for effective detection of any such contamination. Using an array of light emitters separated substantially along a length of the windshield provides a large area of coverage over the windshield. Accordingly, there is a higher likelihood of detecting the contamination early.

The light detector may be arranged to detect the presence of any refracted light directly. An alternative is to monitor the reflected light and determine the presence of refracted light by an intensity drop in the reflected light. Light measured directly is either present or not present. Detecting the presence of reflected light is thus more reliable.

The windshield may be a front windscreen, or a rear windscreen, or a side window. Front and rear windscreens are most likely to benefit from such a monitoring system since any contamination on those windscreens would more greatly affect a driver's vision or distract their attention. Side windows, especially front side windows can also affect a driver's vision.

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

The or each light emitter may comprise a Light Emitting Diode (LED). An LED is relatively cheap and simple compared to other light emitters and emit light over a narrow bandwidth which may be advantageous for detection purposes.

Each light emitter may comprise a pulsar to pulsate, strobe, or shutter the light beam according to a predefined pattern. Pulsating the light beam would provide for a level of noise filtering since any light detected which isn't pulsating according to the predefined pattern would not be attributable to the light emitter.

Each light beam may be pulsated at a unique predefined pattern or may be phase shifted relative to the other light pulse patterns. Each light beam being unique in these ways would allow the emitter and/or the location within the windscreen of the light beam it emits to be identified.

The array may substantially span along a side edge of the windshield. A side edge as opposed to a top or bottom edge would result in fewer light emitters being required to provide equivalent windshield coverage due to the aspect ratio of a windshield.

The light source may comprise two arrays of light emitters, the arrays being mutually orthogonal. Two mutually orthogonal arrays provides for a 2 dimensional co-ordination system which is particularly advantageous when using detectors which have difficulty in distinguishing direction of the source of the light. The 2 dimensional array thus allows for improved fidelity of locating the contamination.

The light detector may comprise a camera arranged to monitor the windshield. The camera may be configured to be sensitive only to the light wavelength, or band of wavelengths produced by the light emitters. Cameras are reliable and easy to install. In addition, location of the contamination can be detected to a relatively high degree of accuracy by associating the location of refracted light with a particular pixel of the camera.

The camera may be arranged to monitor the interior face of the windshield. Any refracted light resulting from interior contamination may thus be detected directly.

The light detector may comprise a photodiode. Photodiodes are cheap and reliable and would be particularly advantageous when used with the 2 dimensional array of light emitters.

The system may comprise an association module arranged to determine a coordinate position of the contamination by associating the light with one or more emitters from each array.

The system may comprise a noise filter to distinguish light emitted from the light emitter from other light. The noise filter thus reduces the risk of false light detections.

The noise filter may comprise a lock-in amplifier. A lock-in amplifier is reliable and easy to integrate.

The angle of incidence of the light beam may be between about 43° and about 65°. The critical angle of a glass to air interface may be about 43° and the critical angle of a glass to water interface may be about 65°. The difference in critical angle is due to the difference in refractive index between air and water. Therefore, the system would detect most water based contamination over this range of incidence angles.

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 element on the windshield; and a control module arranged to control the windshield clearing element to clear the windshield in response to the detection of refracted light.

The windshield clearing element may comprise a heating mechanism. The heating mechanism may comprise a plurality of heating elements, wherein the control module may be arranged to heat a heating element at a location corresponding to the detected contamination.

Each heating element may comprise a resistance heating element. A resistance heating element converts electrical energy to heat energy and are relatively efficient compared to other heating types.

The resistance heating element may comprise a metallic layer. A metallic layer is easy to provide on a windshield for instance by deposition.

The system may comprise a termination module to terminate heating of the heating element in response to the windshield monitoring system ceasing to detect refracted light or after a predetermined time period.

Terminating heating in response to no refracted light being detected provides for an increase of efficiency in terms of power required to power the 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 monitoring a windshield. The method may comprise emitting a plurality of light beams into an edge of the windshield at an incidence angle arranged to subject the light beams to total internal reflection at a windshield to air interface to propagate across the windshield. The angle of incidence may be arranged to refract the light beam away from the windshield at a windshield to contaminant interface. The plurality of light beams may be separated so as to substantially span a length of the windshield. The method may comprise detecting the presence of light refracted away from the windshield.

The method may comprise pulsating and/or strobing of the or each light beam according to a pre-defined pattern.

The method may comprise pulsating, strobing or shuttering each light beam according to a unique pattern.

The method may comprise emitting the plurality of light beams substantially along adjacent mutually orthogonal edges of the windshield.

The method may comprise filtering out noise detected by the light detector.

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

The method may comprise associating the refracted light with one of the light emitters.

According to a further aspect of the present invention there is provided a method of clearing a windshield comprising; detecting surface contamination using the aforementioned method of monitoring a windshield; and heating the windshield in response to detecting any contamination.

The method may comprise dividing the windshield into a plurality of zones and heating the zone corresponding to the location of detected contamination.

The method may comprise terminating the heating of the area in response to ceasing to detect refracted light or after a predetermined time period.

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 A shows a windshield monitoring system according to the prior art; Figure 1 B shows a similar view to Figure 1 A; Figure 2 shows a windshield monitoring system according to an embodiment of the present invention; Figure 3 shows a block diagram of the windshield monitoring system from Figure 2; Figure 4 shows a schematic of a windshield clearing system including the windshield monitoring system from Figure 2; Figure 5 shows a section view of the windshield monitoring system from Figure 2 in operation; Figure 6 shows a similar view to Figure 2 of a windshield monitoring system according to an alternative embodiment of the present invention; and Figure 7 shows a similar view to Figure 3 of an alternative embodiment of the present invention.

DETAILED DESCRIPTION

With reference to Figure 2, a vehicle 100 includes a vehicle frame 102 supporting at least one windshield 104 dividing the vehicle interior and the vehicle exterior. The term windshield covers a front windscreen, a rear windscreen, and a side window. Each windshield 104 either comprises a plurality of sheets of laminated glass or a singular sheet of glass. For instance, a laminated glass windshield 104, as shown in Figure 5, is constructed using an inner sheet of glass 105, an outer sheet of glass 107, and an intermediate layer 109 of Polyvinyl Butyral (PVB) sandwiched between the two. The intermediate layer 109 is made from PVB to prevent shards of glass flying off in a crash and because PVB has the same refractive index as the inner 105 and outer 107 sheets of glass.

The vehicle 100 also includes a windshield monitoring system. Figure 2 shows part of the windshield monitoring system with Figure 3 showing a more detailed version in the form of a block diagram.

With continued reference to Figure 2, the windshield monitoring system includes an array of light emitters 108. The light emitters are provided in the form of Light Emitting Diodes (LEDs). The emitters 108 are separated from one another to span over a length, such that the light they emit spans the width of the 104. The emitters 108 are separated by substantially equidistantly from one another. The emitters 108 are arranged to emit a narrow beam of light 106, specifically narrow beams of monochromatic light. Monochromatic light is used in contrast to white light since white light would disperse within the windshield. The array of emitters 108 is provided along one side of the windshield. In particular, the emitters 108 are encapsulated along the side of the windshield 104 within a refractive index matched medium. As will be described in more detail below, the emitters are arranged to direct the beams of light 106 into the windshield at an angle of inclination of between about 43° and about 65°.

The windshield monitoring system also includes a detector. Specifically, the detector is a camera 110. The camera 110 is a digital camera able to distinguish a position of a detected image by pixels. The camera 110 may be located in the vehicle interior. The camera 110 may be sensitive to all wavelengths of visible light, or may alternatively be sensitive only to a specific wavelength or waveband corresponding to the beams of light produced by the light emitters 108. When monitoring the front windscreen, the camera 110 is integrated into a ceiling panel of the vehicle 100 in between a rear view mirror (not shown) and the windshield 104. Alternatively, the camera may be mounted at the top of the dashboard. The camera is oriented so as to monitor an interior surface 112 of the front windscreen. As will be described in more detail below, the camera 110 can thus detect any refracted light 114 as a result of surface contamination 116. Due to the camera 110 dividing a recorded image up by pixels, the location of the refracted light 114, and thus the location of contamination 116, can be determined directly by mapping the pixel(s) detecting the reflected light onto a map of the windshield 104.

With reference to Figure 3, the example shown of the windshield monitoring system also includes a noise filter 119, which noise filter 119 includes a pulsar 120 and a lock-in amplifier 122. The function of each of these components will be described in more detail below. However in summary, the pulsar 120 includes a motor 124 and a disc 126. The disc is rotatable about an axis (not shown). The motor 124 is coupled to the disc 126 so as to rotate the disc 126 in operation. The disc 126 includes successive transparent 128 and opaque 130 regions. Light from a light beam 106 is allowed to pass though the transparent regions 128. However, light beams 106 are blocked by the opaque regions 130. The axis of rotation of the disc 126 is misaligned with the beam of light 106 such that the beam of light 106 impinges on whichever of the transparent 128 or opaque 130 regions it is aligned with.

As an alternative to pulsating the light beam using the disc 126, the light beam can be pulsated by strobing or shuttering by flickering the light beam on and off using control logic stored in on a computer on board the vehicle.

The lock-in amplifier 122 communicates with the motor 124 so as to obtain the rotational speed of the disc 126. The lock-in amplifier 122 also has a data store having information regarding the geometric profiles of the transparent and opaque regions 128, 130. In this way, the lock-in amplifier can associate light detected as a result of the beam of light 106 from other light 132, for instance natural light or light from oncoming vehicle headlights.

With reference to Figure 4, the vehicle 100 also includes a windshield clearing system 140. The windshield clearing system 140 includes a control module 142 and a heating mechanism 144.

The control module 142 is provided as electronic data on a non-volatile memory component of an on-board vehicle computer. The computer also includes a processor for executing the electronic data. Operation of the control module 142 is described in more detail below. However, the control module 142 receives inputs from the windshield monitoring system.

Specifically, the control module 142 receives an indication as to the presence and location of any detected refracted light 114. The control module 142 then commands a heating zone 144 at a location of the detected refracted light to heat up to clear the responsible contamination.

The control module 142 includes a termination module 145 as part of the electronic data stored on the memory component of the on-board computer. The termination module 145 is arranged to send a termination command to the heating zone 144 to terminate heating in response to the camera 110 (Figure 2) ceasing to detect refracted light 114.

The heating mechanism 144 includes a plurality of active heating elements 146 and passive heating elements 148. The active heating elements 146 include resistance heating elements arranged to increase in temperature when an electrical current is passed across them. The resistance heating elements may be provided as vapour deposited metallic layers. The metallic layers can be fabricated from any metallic element or alloy suitable for conducting heat in by electrical resistance. One such metal allow is an alloy including silver. However, other electrically conductive materials may be used. For instance, an organic material, such as graphene, may be used. The passive elements 148 are boundaries of the active heating elements 146 and are provided as areas of uncoated glass to provide insulated areas intermediate the active heating elements 146. These uncoated areas are relatively narrow so as to prevent a pattern of unclear windshield. It can be visualised that the windshield is thus divided into a plurality of zones by virtue of the active and passive heating elements 146, 148.

With reference to Figure 5, in operation, light from an emitter 108 is shone as a beam of light 106 into an edge of the windshield 104. The light beam 106 is directed into the windshield 104 at an angle of incidence el relative to a normal line of incidence N of the windshield 104.

The angle of incidence (3, is between about 43° and about 65°. It will be appreciated that the windshield in Figure 5 is of a laminated glass construction though the same angles of incidence would be applicable to a windshield made from a singular sheet of glass.

The lower limit of about 43° is chosen since this is the critical angle Bo of a glass to air interface. The critical angle Be is the angle at which light reflects internally with no light escaping from the glass to the air. This phenomenon is known as total internal reflection. Any angle of incidence greater than the critical angle Be also subjects the light beam to total internal reflection. The angle of incidence, being greater than the critical angle of 43° is sufficient to subject the beam of light 106 to total internal reflection at a glass to air interface to propagate the beam of light 106 across the windshield 104 to an opposing edge thereof.

In particular, the light beam 106 is reflected off both interior and exterior surfaces to propagate the light beam 106 across the windshield 104.

The upper limit of about 65° is the critical angle, EU for a glass to water interface. In the same way, a beam of light 106 impinging on a glass to water interface at an angle of incidence, 9, greater than 65° would reflect internally whereas an angle of incidence lower than 65° would refract light away from the windshield 104 as refracted light 114. An initial angle of incidence ei is selected to be lower than the critical angle 6c of glass to water in order to intentionally refract light 114 away from the windshield 104 when in contact with any water based contamination 116. In this way, the angle of incidence 9, is arranged to refract the light beam 106 away from the windshield 104 at a glass to water/contaminant interface.

Water based contamination benefits most from this clearing system since water is more easily cleared up by heating than other types of contamination such as dirt. Water based contamination 116 includes water vapour, liquid water, and ice.

Any refracted light 114 is detected by the camera 110. Any light detected by the camera 110 which has not been pulsated by the pulsar 120 (Figure 3) will be filtered out by the noise filter 119.

Since the camera 110 can distinguish the location of refracted light 114 on the windshield 104, the control module (Figure 4) configures the corresponding active heating element 146 Ocovering the area of contamination 116 to heat up. Heating the area of contamination 116 will evaporate the water responsible for the contamination 116.

The termination module 145 sends a termination command to stop passing electrical current through the active heating element 146 when the camera 110 ceases to detect refracted light 114. In addition, the termination module 145 sends a termination command to stop passing electrical current through the active heating element 146 after a predetermined time period. This is particularly important in instances where false positives occur. For instance, a false positive may be triggered for windshield defects such as chips or cracks which will never been cleared by any of the vehicle's on board ancillary systems. Providing the termination command after the predetermined time period thus prevents wasted energy for non-treatable windshield contamination scenarios.

The advantages of the previous embodiment are numerous. One particular advantage is that by providing detection over a wide area of the windshield 104, less energy is ultimately consumed since any contamination 116 is detected early. This is particularly important for electric or hybrid electric vehicles where power consumption is critical to the range of the vehicle. In addition, dividing the windshield into zones of separate heating elements provides further efficiencies since uncontaminated areas are not directly heated.

With reference to Figures 6 and 7, an alternative embodiment of the windshield monitoring system will now be described. Figure 6 shows part of the windshield monitoring system with Figure 7 showing a more detailed version in the form of a block diagram. It is possible to transfer those features described specifically with reference to one embodiment to the other embodiment. Those features of the alternative embodiment which are common to the previous embodiment are labelled 100 greater.

The windshield monitoring system includes two arrays of emitters 208. The arrays are mutually orthogonal and are provided along adjacent edges of the windshield 204.

Specifically, the arrays are positioned along a bottom edge and a right side edge of the windshield 204. The emitters 208 are again separated so as to span along each edge of the windshield to provide coverage over the majority of the windshield 204. The emitters 208 are oriented to emit beams of light 206 into the windshield 204 at an angle of incidence of between about 43° and about 65°. These angles are selected for the same reasons as describes above. The emitters 208 are also oriented so that the light beams 206 are substantially parallel.

The light detector in this embodiment is a photodiode 210 as opposed to a camera. The photodiode 210 can detect the presence of light, and depending on the type of photodiode used, may tuned to be sensitive only to a specific wavelength or band of wavelengths of light as may be produced by the light emitters, but cannot distinguish the location of light, like the camera 110. In order to determine the location of contamination 216, the windshield detection system associates the detected light with one light emitter 208 from each array.

With reference to Figure 7, the windshield monitoring system again includes a pulsar 220 and a lock-in amplifier 222 which work in the same way as the previous embodiment. However, each light beam 206 is pulsated at a unique predefined pattern and/or frequency of pulsation. The windshield monitoring system also includes an association module 270. The association module 270 is provided as electronic data on the memory component of the on-board computer, like the control module.

The association module 270 includes a data store for storing data relating to the pulse patterns for each emitter 208. In response to the photodiode 210 detecting a light pulse, the association module 270 compares the pulsed refracted light beam with those stored for each emitter 208. By matching the light pulse to the responsible emitter 208 in each array, the association module locates the position of the contamination 216 with a 2 dimensional coordinate. For instance, the association module may determine that contamination exists in the centre of the windshield 204 if a central emitter 208 from each array is identified as being responsible for the refracted light 214 (Figure 6). This coordinate is then fed into the control module (Figure 4) to control a heating zone corresponding to an area at which contamination 216 has been detected.

As an alternative to pulsating the light beam 206, the light beams 206 could be phase shifted relative to the other beams of light 206.

Claims

CLAIMS1. A windshield monitoring system, comprising a plurality of light emitters forming an array, each emitter arranged to direct a beam of light into an edge of a vehicle windshield at an angle of incidence 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 to an opposing edge thereof, the angle of incidence being arranged to refract the light beam away from the windshield at a windshield to contaminant interface; and a light detector arranged to detect that light from the beam of light has been refracted away from the windshield; wherein the emitters are separated substantially across a length of the windshield.
2. The system of Claim 1 wherein the light detector is arranged to detect the presence of any refracted light directly.
3. The system of Claim 1 wherein the windshield is a front windscreen, or a rear windscreen, or a side window.
4. The system of Claim 1 or Claim 2 wherein the contamination is selected from the list of moisture, ice, and liquid water.
5. The system of any preceding claim wherein the or each light emitter comprises a Light Emitting Diode (LED).
6. The system of any preceding claim wherein each light comprises a pulsar to pulsate the light beam according to a predefined pattern.
7. The system of Claim 6 wherein each light beam is pulsated, strobed or shuttered at a unique predefined pattern or is phase shifted relative to the other light pulse patterns.
8. The system of any preceding claim wherein the array substantially spans along a side edge of the windshield.
9. The system of any preceding claim wherein the light source comprises two arrays of light emitters, the arrays being mutually orthogonal.
10. The system of any preceding claim wherein light detector comprises a camera arranged to monitor the windshield.
11. The system of Claim 10 wherein the camera is arranged to monitor the interior face of the windshield.
12. The system of Claim 9 wherein the light detector comprises a photodiode.
13. The system of Claim 12 comprising an association module arranged to determine a coordinate position of the contamination by associating the light with one or more emitters from each array.
14. The system of any preceding claim comprising a noise filter to distinguish light emitted from the light emitter from other light.
15. The system of Claim 14 wherein the noise filter comprises a lock in amplifier.
16. The system of any preceding claim wherein the angle of incidence of the light beam is between about 43° and about 65°.
17. A windshield clearing system comprising; the windshield monitoring system of any preceding claim; a windshield clearing element on the windshield; and a control module arranged to control the windshield clearing element to heat the area corresponding to an area of the windshield where light has been refracted.
18. The windshield clearing system of Claim 17 wherein the windshield clearing element comprises a heating mechanism.
19. The windshield clearing system of Claim 18 wherein the heating mechanism comprises a plurality of heating elements, wherein the control module is arranged to heat a heating element corresponding to the location of the detected contamination.
20. The system of Claim 19 wherein the heating element comprises a resistance heating element.
21. The system of Claim 20 wherein the resistance heating element comprises a metallic layer.
22. The system of any of Claims 17 to 21 comprising a termination module to terminate heating of the heating element in response to the windshield monitoring system ceasing to detect refracted light or after a predetermined time period.
23. A windshield for a vehicle or vehicle comprising a system as claimed in any preceding claim.
24. A method of monitoring a windshield, comprising; emitting a plurality of light beams into an edge of the windshield at an incidence angle arranged to subject the light beams to total internal reflection at a windshield to air interface to propagate across the windshield and the angle of incidence being arranged to refract the light beam away from the windshield at a windshield to contaminant interface, the plurality of light beams being separated so as to substantially span a length of the windshield; and detecting the presence of light refracted away from the windshield.
25. The method of Claim 24 comprising pulsating, strobing, or shuttering the or each light beam according to a pre-defined pattern.
26. The method of Claim 25 comprising pulsating, strobing or shuttering each light beam according to a unique pattern.
27. The method of any of Claims 24 to 26 comprising emitting the plurality of light beams substantially along adjacent mutually orthogonal edges of the windshield.
28. The method of any of claims 24 to 27 comprising filtering out noise detected by the light detector.
29. The method of Claim 26 or any claim dependent thereon comprising associating the refracted light with one of the light emitters.
30. A method of clearing a windshield comprising detecting surface contamination using the method of any of claims 24 to 29 and heating an area of the windshield in response to detecting any contamination.
31. The method of Claim 30 comprising dividing the windshield into a plurality of zones and heating a zone corresponding to the location of detected contamination.
32. The method of Claim 31 comprising terminating heating of the area in response to ceasing to detect refracted light or after a predetermined time period.
33. A windshield monitoring system, a windshield clearing system, a vehicle, a method of monitoring on a windshield, or a method of clearing a windshield as substantially described herein with reference to figures 2 through 7.