WO1999024288A1

WO1999024288A1 - Antidazzle polarized lighting system for vehicles

Info

Publication number: WO1999024288A1
Application number: PCT/IB1998/001770
Authority: WO
Inventors: Nicola Ripoli
Original assignee: LENOCI ANTONIO
Current assignee: LENOCI ANTONIO
Priority date: 1997-11-06
Filing date: 1998-11-05
Publication date: 1999-05-20
Anticipated expiration: 2000-05-06
Also published as: AU9639798A; ITMI972479A1; IT1296068B1

Abstract

The invention relates to an lighting system for vehicles which comprises a polarized light emitting unit and a filtering unit which is arranged between the emitting unit and an observer and is polarized at about 90 DEG C with respect to the light supplied by said emitting unit. The filtering unit may be integrated into the windscreen of a motor vehicle or into the lenses of glasses worn by the observer.

Description

"ANTIDAZZLE POLARIZED LIGHTING SYSTEM FOR VEHICLES"

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The present invention relates to an lighting system for vehicles. In particular it relates to an anti-dazzle lighting system, which is used most advantageously in the presence of fog or other similar adverse weather conditions.

It is known that, in adverse weather conditions, for example at night-time and/or when there is rain or fog, the visibility which is achieved by means of the conventional lighting systems for vehicles (for example, motor vehicles, motorcycles, etc.) is often inadequate. This is due, in addition to the limited lighting capacity of the headlamps, mainly to the effect of the light refracted by the water droplets suspended in the atmosphere, which spreads creating a diffused light which greatly disturbs correct vision of the road and obstacles. Moreover, often, in these conditions the driver of the vehicle is obliged to switch the headlights to the so-called "full-beam" condition which, in addition to worsening the problems resulting from the refraction of light, may also cause blinding of the drivers of vehicles approaching on the opposite side of the road, so much so that the highway code stipulates specific penalties for those persons which use full-beam headlights in conditions which are dangerous for other drivers.

For a long time a solution to these problems has been sought, resulting, however, in the adoption of technical measures which help improve the visibility, but do not solve the underlying cause of these problems.

For example, so-called "anti-fog lamps" are illuminating lamps which emit a light of suitable wavelength - very often yellow in colour - and are situated at a short distance from the road surface so as to reduce the effect of refraction at the level of the driver's vision. However, this device is not entirely satisfactory because, beyond a certain luminous intensity, it results in blinding both of the driver him/herself and the drivers of the vehicles approaching in the opposite direction. Moreover, in vei y foggy conditions it loses most of its effectiveness.

Therefore the only solution which to date is still the safest is that of drastically reducing the speed of the vehicle, so as to adapt the speed to the actual conditions of visibility.

The object of the present invention is therefore that of eliminating the abovementioned drawbacks by providing a device which solves the underlying problem of dazzling refracted light.

Such an object is achieved by an lighting system for vehicles which comprises a unit, emitting polarized light and a filtering unit which is arranged between the emitting unit and a driver, polarized substantially at 90° with respect to the light from said emitting unit.

According to another aspect of the invention, the same object is achieved by using polarized light for fixed street lighting, where a filter polarized at about 90° with respect to said polarized light is located between the observer and the polarized light source. Further characteristic features and advantages of the device according to the invention will emerge, however, more clearly from the detailed description which follows, taken with reference to the accompanying drawing which shows an example of embodiment of the invention illustrating the principle of operation thereof. The system according to the invention is comprised of two units: an emitting unit A, which emits polarized light, and a filtering unit B, which is located between the unit A and an observer and is polarized substantially at 90° with respect to the plane of polarization of the light emitted by the unit A. For example, the emitting unit A is embodied in the illuminating device of a motor vehicle 1 and the filtering unit B consists of a filter located on the windscreen of the motor vehicle 1 and/or of another motor vehicle 2.

The unit A may be a polarized light source or may be a normal light source, with random polarization, which is polarized downstream, for example by means of a polarizing screen, a refraction polarizer or a Nicol prism.

The unit B may be a dichroic polarizing screen, but preferably consists of a device with liquid crystals which allow the polarization plane to be varied, when by this letter can be adapted to the polarization conditions of the incident light. For this purpose a device controlling the liquid-crystal filter, which intervenes automatically or upon operation by the driver, may be provided; if necessary this would allow the filtering effect to be deactivated entirely, making the polarization plane of the filter parallel with that of the incident light, when this is required.

The system according to the invention exploits the principle whereby polarized light, which passes through a filter polarized at 90° with respect thereto, is almost entirely absorbed (typical absorption values are of the order of 99.95%). Therefore the direct light (continuous lines in the Figure) from the emitting unit A is completely absorbed by the filtering unit B before reaching the observer. A first object of the invention is therefore achieved: the dazzling light directed from the vehicle 1 towards the vehicle 2 may be substantially eliminated, passing through the unit B of the vehicle 2, thus eliminating the danger of blinding of the driver of the vehicle 2.

Any observer, in particular the driver of the vehicle 1 , nonetheless perceives the light diffused and reflected by the illuminated objects, since, advantageously, the light which is reflected (phantom lines in the figure) for example by the road surface or by an obstacle 3, loses partly its polarization (i.e. is polarized randomly) and therefore is able to pass in part through the unit B and be visible to the observer him/herself.

In this process, the overall luminous intensity emitted by the emitting unit A is mostly filtered. However, there is no possibility that the luminous intensity perceived by the observer will be insufficient to ensure good visibility, since the intensity of the stimulus detected by the human organism is proportional to the logarithm of the luminous intensity striking the eye: therefore, even a substantial reduction in the luminous intensity reaching the observer will not influence to the same extent the intensity actually perceived by the human eye.

Synergistic with the effect described above, there is also an advantage associated with the fact that the observer is able to see also in the dark whether the vehicle approaching in the opposite direction has a normal attitude or is swerving dangerously (for example because it is skidding or because it has entered a bend at high speed): in fact, following inclination on the roll axis of the vehicle, the polarization plane of the light emitted by the vehicle itself varies its inclination and therefore will be more or less efficiently filtered by the filtering unit situated opposite the observer who will perceive a variable luminous intensity. This type of information may be advantageously interpreted by the observer as an indication of danger (for example because the road surface is in very bad condition) .

A further fundamental advantage of the invention consists in the fact that the light which is refracted (dotted lines in the figure) by the water droplets 4 (fog, rain, etc.), or in any case by isotropic substances, retains instead mostly the same polarization as the incident light and therefore is entirely filtered by the filtering unit B.

Therefore another object of the invention is also achieved: the light which is refracted by the water droplets is no longer visible to the observer and therefore no longer produces the troublesome phenomenon of diffused light mentioned above, providing excellent visibility even in night-time conditions where there is rain and fog.

Preferably the filtering unit B is vertically polarized so that the bothersome reflections due to the natural light striking horizontal flat surfaces are also eliminated; in this case, for correct operation of the system, the emitting unit A must emit vertically polarized light.

A general example may provide an indication of the advantages associated with this preferred embodiment. Natural non-polarized light striking specular surfaces is reflected polarized in a plane parallel to the surface itself. Therefore, stretches of water, owing to their horizontal nature, reflect horizontally polarized light , which is completely absorbed by the unit B only if it is polarized vertically.

According to another embodiment of the invention, the lighting system may be manufactured very economically by simply fitting a polarizing screen to the ordinary headlamps of a motor vehicle and providing the driver with suitable glasses having lenses which are polarized at 90° with respect to the polarizing screen of the headlamps.

Finally, for the sake of convenience of use, the filtering unit could be integrated into the sun screen which is commonly provided in all motor vehicles: this embodiment has the advantage that it leaves the driver free to use the system only when desired.

It is understood that the invention may assume other embodiments, all of which fall within the teachings thereof and which must be regarded as included within the scope of the present invention. For example a possible application could consist in a public lighting system, where the street illuminating lamps emit polarized light, while the vehicles have suitable polarized filters located opposite the driver.

Finally the invention may be used not only on land vehicles, but also on boats and planes (in particular during ground handlings) which have to operate in conditions of poor visibility.

Claims

1 ) Lighting system for vehicles, characterized in that it comprises a polarized light emitting unit and a filtering unit which is arranged between the emitting unit and an observer and is polarized substantially at 90° with respect to the light supplied by said emitting unit.

2) Lighting system as claimed in Claim 1 , in which said emitting unit is the lighting system of the vehicle, which has a polarized light source.

3) Lighting system as claimed in Claim 1 , in which said emitting unit is the lighting system of the vehicle to which a polarizing screen is fitted.

4) Lighting system as claimed in Claim 1 , in which said emitting unit is the lighting system of the vehicle to which a Nicol prism is fitted.

5) Lighting system as claimed in any one of the preceding claims, in which said filtering unit is integrated into the windscreen of a vehicle.

6) Lighting system as claimed in Claim 5, in which said windscreen comprises a polarized filter of the liquid-crystal type.

7) Lighting system as claimed in Claim 6, in which said liquid crystals are orientable and said polarized filter also comprises a device for controlling the polarization plane.

8) Lighting system as claimed in any one of Claims 1 to 4, in which said filtering unit is formed in a portion of a sun screen of the vehicle.

9) Lighting system as claimed in any one of Claims 1 to 4, in which said filtering unit is integrated into lens of glasses, which are worn by the observer.

10) Lighting system as claimed in any one of the preceding claims, in which the emitting unit emits vertically polarized light and the filtering unit is horizontally polarized. 1 1 ) Street lighting system, characterized in that it comprises a polarized light emitting unit and also a filtering unit which is arranged between the emitting unit and an observer and is polarized substantially at 90° with respect to the light supplied by said emitting unit.

12) Use of polarized light for street lighting, characterized in that a filter polarized at about 90° with respect to said polarized light is arranged between the observer and a polarized light source.