GB2134466A

GB2134466A - Anti-dazzle arrangements for vehicles

Info

Publication number: GB2134466A
Application number: GB08402480A
Authority: GB
Inventors: John Bottrill
Original assignee: Britax PMG Ltd
Current assignee: Britax PMG Ltd
Priority date: 1983-02-11
Filing date: 1984-01-31
Publication date: 1984-08-15
Also published as: GB8402480D0

Abstract

The reflective layer 14 of a rearview mirror 12 for a motor vehicle is covered by a filter 16 having a band-pass transmittance characteristic with a peak in the range between 550 and 650 nm. This coincides with the peak of sensitivity of the human eye and thus serves to reduce dazzle from headlamps of following vehicles. <IMAGE>

Description

setcI ILATlUN Anti-dazzle arrangements for vehicles This invention relates to anti-dazzle arrangements for vehicles and more particularly to arrangements for reducing dazzle from the headlamps of other vehicles. The invention has particular but not exclusive application to the reduction of dazzle from the images of the headlamps of following vehicles produced by rear view mirrors.

It has already been proposed to reduce dazzle from the headlamps of other road users by forming the headlamp lenses, windscreens and rear windows of motor vehicles from a material which transmits plane polarised light, the direction of polarisation being inclined at 45 degrees to the horizontal. The direction of inclination of the plane of polarisation is the same for the windscreen and the headlamp lenses and opposite for the rear window. The result is that a driver can perceive, through his windscreen, objects illuminated by his own headlamps. On the other hand, light from the head lamps of oncoming vehicles is polarised in the opposite direction to that which is passed by the windscreen and light from the headlamps of following vehicles is polarised in the opposite direction to that which is passed by the rear window.However, this system requires at least the headlamps of all vehicles to be equipped to produce light polarised in accordance with an agreed convention. The present invention is concerned with an arrangement which does not require the provision of special equipment on other vehicles.

Patent Specification GB 1 506028 discloses the formation of the windows of vehicles from a material which has a higher transmission in the long wave region than in the short wave region and which falls sharply in the ultraviolet region. While this approach can be used to reduce the glare produced by daylight, it has no effect on dazzle from the headlamps of other vehicles.

According to the invention, a light-transmitting member adapted to be interposed between light incident on the exterior of a vehicle and the eyes of a driver of the vehicle comprises a filter arranged to absorb light of wavelength in the range from 500 to 650 nm. and to transmit light of both longer and shorter wavelengths.

The pass-band of the filter may be limited to a the range of 550 to 650 nm.

In one form of the invention, the filter is arranged to cover the reflective surface of a rear view mirror. However, filters in accordance with the invention may alternatively or additionally be incorporated into some or all of the vehicle windows, including the windscreen.

The invention will be better understood from the following description, with reference to the accompanying drawings, in which: Figure 1 is a graph showing the spectral sensitivity of the human eye as a solid line and the variation of intensity with wavelength of the light from a tungsten-halogen vehicle headlamp as a chain-dotted line; Figure 2 is a graph showing the variation of percentage transmittance with wavelength of a filter in accordance with the invention; and Figure 3 is a cross-sectional view of an interior rear view mirror in accordance with the invention.

The radiation produced by a tungsten-halogen vehicle headlamp has maximum intensity at a wavelength of about 800 nm. The human eye is most sensitive to a light over a relatively narrow wavelength band centered on 550 nm. Consequently, a filter having a transmittance characteristic as illustrated in Fig. 2, i.e. absorbing light in a narrow band of approximately 100 nm. width centred on a wavelength of 600 nm., will absorb a large proportion of that part of the radiation from a tungsten-halogen headlamp to which the eye is particularly sensitive. This wavelength band is sufficiently narrow for the filter not to significantly reduce the intensity of red light, for exampie from traffic signals and vehicle brake lights, or amber light, for example from traffic lights and vehicle direction indicators.

Turning to Fig. 3, an interior mirror comprises a case 10 containing a glass substrate 1 2 with a reflective layer 1 4 on its front surface. Adhered to the front of the reflective layer 14 is a filter 16, formed of polyester or polycarbonate and having a transmittance characteristic in accordance with Fig. 2.

Alternatively, the reflective layer 1 4 could be replaced by a reflective layer on the second surface of the glass substrate 1 2. A further alternative would be to incorporate the material of the filter into an adhesive used to secure two glass layers to one another. Theoretically, it would be possible to deposit a reflective layer directly on to the second surface of a filter but it will usually be more satisfactory to use a glass substrate to form the necessary optically flat surface for the reflective layer.

The filter 1 6 may be either a filter devised to be the reverse of the tungsten light source intensity, such as the filter 80B manufactured by Lee Filters (Developments) Limited of Andover, England or the reverse of the human eye response such as the filter CC40G, also manufactured by Lee Filters (Developments) Limited.

1. A light-transmitting member adapted to be interposed between the light incident on the exterior of a vehicle and the eyes of a driver of the vehicle, comprising a filter arranged to absorb light of wavelength in the

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. setcI ILATlUN Anti-dazzle arrangements for vehicles This invention relates to anti-dazzle arrangements for vehicles and more particularly to arrangements for reducing dazzle from the headlamps of other vehicles. The invention has particular but not exclusive application to the reduction of dazzle from the images of the headlamps of following vehicles produced by rear view mirrors. It has already been proposed to reduce dazzle from the headlamps of other road users by forming the headlamp lenses, windscreens and rear windows of motor vehicles from a material which transmits plane polarised light, the direction of polarisation being inclined at 45 degrees to the horizontal. The direction of inclination of the plane of polarisation is the same for the windscreen and the headlamp lenses and opposite for the rear window. The result is that a driver can perceive, through his windscreen, objects illuminated by his own headlamps. On the other hand, light from the head lamps of oncoming vehicles is polarised in the opposite direction to that which is passed by the windscreen and light from the headlamps of following vehicles is polarised in the opposite direction to that which is passed by the rear window.However, this system requires at least the headlamps of all vehicles to be equipped to produce light polarised in accordance with an agreed convention. The present invention is concerned with an arrangement which does not require the provision of special equipment on other vehicles. Patent Specification GB 1 506028 discloses the formation of the windows of vehicles from a material which has a higher transmission in the long wave region than in the short wave region and which falls sharply in the ultraviolet region. While this approach can be used to reduce the glare produced by daylight, it has no effect on dazzle from the headlamps of other vehicles. According to the invention, a light-transmitting member adapted to be interposed between light incident on the exterior of a vehicle and the eyes of a driver of the vehicle comprises a filter arranged to absorb light of wavelength in the range from 500 to 650 nm. and to transmit light of both longer and shorter wavelengths. The pass-band of the filter may be limited to a the range of 550 to 650 nm. In one form of the invention, the filter is arranged to cover the reflective surface of a rear view mirror. However, filters in accordance with the invention may alternatively or additionally be incorporated into some or all of the vehicle windows, including the windscreen. The invention will be better understood from the following description, with reference to the accompanying drawings, in which: Figure 1 is a graph showing the spectral sensitivity of the human eye as a solid line and the variation of intensity with wavelength of the light from a tungsten-halogen vehicle headlamp as a chain-dotted line; Figure 2 is a graph showing the variation of percentage transmittance with wavelength of a filter in accordance with the invention; and Figure 3 is a cross-sectional view of an interior rear view mirror in accordance with the invention. The radiation produced by a tungsten-halogen vehicle headlamp has maximum intensity at a wavelength of about 800 nm. The human eye is most sensitive to a light over a relatively narrow wavelength band centered on 550 nm. Consequently, a filter having a transmittance characteristic as illustrated in Fig. 2, i.e. absorbing light in a narrow band of approximately 100 nm. width centred on a wavelength of 600 nm., will absorb a large proportion of that part of the radiation from a tungsten-halogen headlamp to which the eye is particularly sensitive. This wavelength band is sufficiently narrow for the filter not to significantly reduce the intensity of red light, for exampie from traffic signals and vehicle brake lights, or amber light, for example from traffic lights and vehicle direction indicators. Turning to Fig. 3, an interior mirror comprises a case 10 containing a glass substrate 1 2 with a reflective layer 1 4 on its front surface. Adhered to the front of the reflective layer 14 is a filter 16, formed of polyester or polycarbonate and having a transmittance characteristic in accordance with Fig. 2. Alternatively, the reflective layer 1 4 could be replaced by a reflective layer on the second surface of the glass substrate 1 2. A further alternative would be to incorporate the material of the filter into an adhesive used to secure two glass layers to one another. Theoretically, it would be possible to deposit a reflective layer directly on to the second surface of a filter but it will usually be more satisfactory to use a glass substrate to form the necessary optically flat surface for the reflective layer. The filter 1 6 may be either a filter devised to be the reverse of the tungsten light source intensity, such as the filter 80B manufactured by Lee Filters (Developments) Limited of Andover, England or the reverse of the human eye response such as the filter CC40G, also manufactured by Lee Filters (Developments) Limited. CLAIMS

1. A light-transmitting member adapted to be interposed between the light incident on the exterior of a vehicle and the eyes of a driver of the vehicle, comprising a filter arranged to absorb light of wavelength in the range from 500 to 650 nm. and to transmit the light of both longer and shorter wavelengths.

2. A light-transmitting member according to claim 1, wherein the pass-band of the filter has a the range of 550 to 650 nm.

3. A light-transmitting member according to claim 1 or 2, substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

4. A rearview mirror for a motor vehicle, having a filter in accordance with claim 1, 2 or 3, covering its reflective surface.

5. A window for a motor vehicle incorporating a filter according to claim 1, 2 or 3.

5. A rearview mirror for a motor vehicle substantially as hereinbefore described with reference to Fig. 3 of the accompanying drawings.