WO1991007674A1

WO1991007674A1 - Anti-dazzle filter

Info

Publication number: WO1991007674A1
Application number: PCT/GB1990/001771
Authority: WO
Inventors: Alan Mosley; Michael Charles Keogh Wiltshire
Original assignee: General Electric Company PLC
Current assignee: General Electric Company PLC
Priority date: 1989-11-17
Filing date: 1990-11-16
Publication date: 1991-05-30
Anticipated expiration: 1992-05-17
Also published as: GB8926055D0; AU6729990A; GB9024986D0; GB2238882A

Abstract

An anti-dazzle filter (1) comprises a transparent substrate (2) to which are laminated a vertical polariser (3) and a yellow filter (4). The device may be incorporated into sunglasses or into a visor to reduce glare caused by bright sunlight. Alternatively, it may be used to reduce light back-scattered by fog or mist.

Description

Anti-Dazzle Filter

This Invention relates to a device for reducing dazzle caused by adverse weather conditions including bright sunlight, and in particular to spectacles or a visor for reducing such dazzle.

The problem of dazzle which occurs 1n bright sunlight is due, in particular to the high content of blue light in the sunlight. Glare which occurs in foggy or misty conditions is due to the fact that light from vehicle lamps 1s scattered by the water droplets in the mist or fog, and an appreciable amount is back-scattered Into the eyes of the driver or pilot. This effect is particularly troublesome at night, and leads to reduced vision and fatigue.

Some relief from dazzle from sunlight has previously been obtained by the use of sunglasses incorporating polarising material. A previous solution to the fog or mist problem involves the use of yellow-coloured fog lights mounted low on the vehicle. This solution 1s, however, relatively expensive and is not completely satisfactory.

An object of the present Invention is to provide a cheap and effective device for reducing glare caused by such adverse weather conditions.

SUBSTITUTESHEET According to the invention, there is provided a device for reducing dazzle caused by adverse weather conditions, the device comprising, in combination, a yellow filter and a vertical linear polariser.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which

Figure 1 is a schematic cross-sectional view of a light-reducing device in accordance with the invention,

Figure 2 is a schematic diagram illustrating the operation of the device of Figure 1 for reducing dazzle caused by sunlight, and

Figure 3 is a schematic diagram illustrating the operation of the device of Figure 1 for reducing glare caused by fog or mist. Referring to Figure 1, a light-reducing device 1 comprises a transparent substrate 2 supporting a vertical polariser 3 and a yellow filter 4. Suitable materials for forming the polariser 3 and the filter 4 are, for example, materials designated LLY2-82-75 and LLY1-81-40, both available from Sanritzu of Japan. Alternative yellow filter and polariser materials may, of course, be used. If the polariser and filter combination is sufficiently rigid, the substrate 2 may be dispensed with.

Referring to Figure 2, the device 1 operates as follows to reduce glare from sunlight. Light 5 from a source 6, which may be, for example, a reflection from a road surface or from a beach, reaches the eyes 7 of a person. The light comprises red, yellow, green and blue light components, with a preponderance of blue light, especially on cloudless days. The light is likely to be horizontally polarised by reflection from the generally horizontal surface. If the device 1 is positioned between the source 6 and the eyes 7, the light passes through the substrate 2 of the device and reaches the polariser 3. The polariser has its absorption axis in the horizontal direction and so will transmit only that portion of the light which is vertically polarised. Horizontally-polarised vlsible light of all frequencies is stopped by the polariser 3.

The substantially verti cally-pol ari sed light which has passed through the polariser 3 then reaches the fi lter 4. Of this light, only l i ght in the yellow region of the spectrum passes through the fi lter, and light of higher frequency (shorter wavelength) i s not transmitted. Hence, only light of longer wavelength reaches the eyes 7 of the person.

The devi ce may be incorporated into sunglasses and may be especially useful for use by a driver i n bright sunlight conditions.

Referring to Figure 3, the device 1 operates as follows to reduce glare due to fog or mist. A beam of light 8 is di rected forwards from a li ght source 9 below the eye level of the driver or pilot. If light from the beam 8 hits fog 10, a portion 11 of the li ght i s reflected into the eyes 12 of the dri ver. The amount of reflected light that reaches the eyes of the driver is reduced by the glare-reducing device 1.

The light beam 8 is made up of red, yellow, green and blue (RYGB) light components of different wavelengths, and these components react differently when they hit the individual water droplets 13 in the fog 10. The back-scattered light is sti ll made up of white (RYGB) l ight, but si nce the headli ghts are bel ow the eye level of the driver or pilot the back-scattered light will be partially l i nearly polari sed in the horizontal di rection. The light 11 therefore has a higher proportion of light with horizontal polari sation 14 than li ght with vertical polari sation 15. The l ight passes through the substrate 2 of the device and reaches the polariser 3. The polari ser will transmit only that portion of the light which 1s vertically polarised. Horizontally-polarised light of all frequencies 1s, as descri bed above, stopped by the polariser, and the yellow filter cuts out the light components of higher frequency. The latter is advantageous at night because the human eye 1s less sensitive to yellow light when subjected to low light levels. This effect is described by the photoplc and scotopic eye response curves. The device 1 may be incorporated into a visor for spectacles or for a windscreen, which may be moved away when not in use. Alternatively, the device may be incorporated into spectacles. It may be provided as, or in combination with, the lenses themselves or may be provided separately for clipping on to an existing pair of spectacles.

SUBSTITUTESHEET

Claims

1. A device (1) for reducing dazzle caused by adverse weather conditions, the device comprising, in combination, a yellow filter (4) and a vertical linear polariser(3).

2. A device as claimed in Claim 1, wherein the filter/polariser combination (3,4) is incorporated in a visor which can be placed in position when required.

3. A device as claimed in Claim 1, wherein the filter/polariser combination (3,4) is incorporated into a pair of spectacles.

4. A device as claimed in Claim 1 or Claim 2, adapted for attachment to a pair of spectacles.