GB2115573A

GB2115573A - Mirrors e.g. vehicle rear view mirrors

Info

Publication number: GB2115573A
Application number: GB08205189A
Authority: GB
Inventors: Louis Weatherill
Original assignee: Individual
Current assignee: Individual
Priority date: 1982-02-22
Filing date: 1982-02-22
Publication date: 1983-09-07
Also published as: GB2115573B

Abstract

A mirror comprises a layer of glass (2) which is silvered on one face to provide a reflective surface (4), the other face has a transparent layer of photochromic material (6). In use, for example as a rear view mirror in a motor vehicle, the layer (6) will become darker when the headlights of a following car shine on it, thus reducing glare for the driver. <IMAGE>

Description

SPECIFICATION Mirrors This invention relates to mirrors, and particularly, although not exclusively, to rear-view mirrors for motor vehicles.

When driving at night, the glare from the headlights of a following car is a nuisance and can be a hazard. It is known to provide so-called "dipping" mirrors which can be tilted from a normal viewing position into a "dipped" position which provides an altered reflected image. However, the driver has to take one hand off the steering wheel each time the mirror is to be tilted between these two positions. These can be dangerous, particularly if the driver is already suffering from headlight glare from the following vehicle. Furthermore, the mirror can easily be knocked out of alignment when it is being operated. Also, it is easy to forget to return the mirror to the normal position when the source of glare has gone.

According to the present invention, there is provided a mirror comprising a reflective surface and a transparent layer disposed over the reflective surface, the transparent layer being made from a photomorphic material whereby an increase in the intensity of light incident on the mirror results in an increase in the opacity of the transparent layer.

With the mirror constructed in accordance with the present invention, the intensity of the reflected image varies in inverse proportion to the intensity of light incident on it. Thus, in normal night-driving conditions, the transparent layer would be substantially clear, but it would automatically become darker in response to the headlights of a following vehicle.

The mirror may comprise simply a rigid sheet of photomorphic material, such as glass, of which one surface is silvered to provide the reflective surface. Alternatively, the mirror may comprise a sheet of clear glass of which one surface is silvered and the other surface is provided with a relatively thin layer of photomorphic material, such as glass or plastics material. It may thus be possible to convert existing mirrors by applying such a sheet to the front face.

Thus, a further aspect of the present invention provides a method of modifying an existing mirror, the method comprising applying a layer of photomorphic material to the front face of the mirror.

It will be appreciated that light incident on the mirror will pass through the transparent layer of photomorphic material twice, i.e. once on incidence and once on reflection. This means that the opacity of the transparent layer (dependent on the optical properties of the photomorphic material and on the thickness of the layer) does not have to be as great as would be required if the light were to pass only once through the transparent layer. Furthermore, if only a thin sheet of photomorphic material is used, it does not need to be of high optical quality.

Although the present invention is primarily concerned with rearview mirrors for motor vehicles, mirrors in accordance with the present invention could be useful for other purposes, such as in remote welding or furnace viewing systems.

For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, which shows a cross-section through a mirror.

The mirror shown in the drawing comprises a clear glass sheet 2 which is provided with a layer of silvering 4 on one face so as to render that face reflective. The other face of the glass 2 is provided with a transparent layer 6 of photomorphic material whose opacity increases with increasing intensity of light falling upon it. The glass 2, with its two layers 4 and 6, is mounted in a support 8.

In use of the mirror as the rear-view mirror in a motor car, the photomorphic layer 6 will become darker when, for instance, the headlights of a following vehicle shine upon it. This will reduce the glare of the headlights reflected from the mirror into the eyes of the driver.

The photomorphic layer 6 may comprise a sheet which is loosely fitted to the front surtace or bonded thereto, or it may be sputtered or floated onto the surface of the glass 2.

In order to avoid the effects of excessive darkening of the photomorphic layer 6 during normal daylight conditions, it may be desirable for this layer 6 to be removable from the face of the glass 2. Thus, the layer 6 may comprise a screen which is hinged to the rest of the mirror so that it can be pivoted out of the way when not required, for example when driving in daylight. The screen could then be hinged in front of the mirror only when driving at night.

Claims

1. A mirror comprising a reflective surface and a transparent layer disposed over the reflective surface, the transparent layer being made from a photochromatic material whereby an increase in the intensity of light incident on the mirror results in an increase in the opacity of the transparent layer.

2. A mirror as claimed in claim 1, in which a transparent layer of non-photochromic material is disposed between the reflective surface and the transparent layer of photochromic material.

3. A mirror as claimed in claim 2, in which the transparent layer of non-photochromic material is silvered on one face to provide the reflective surface, the other face being provided with the layer of photochromic material.

4. A mirror as claimed in claim 2 or 3, in which the layer of photochromic material comprises a sheet of plastics material.

5. A mirror as claimed in any one of claims 2 to 4, in which the layer of photochromic material is displaceable relatively to the layer of non-photo chromic material from a use position overlying the layer of non-photochromic material to a non-use position.

6. A mirror as claimed in claim 5, in which the

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Mirrors This invention relates to mirrors, and particularly, although not exclusively, to rear-view mirrors for motor vehicles. When driving at night, the glare from the headlights of a following car is a nuisance and can be a hazard. It is known to provide so-called "dipping" mirrors which can be tilted from a normal viewing position into a "dipped" position which provides an altered reflected image. However, the driver has to take one hand off the steering wheel each time the mirror is to be tilted between these two positions. These can be dangerous, particularly if the driver is already suffering from headlight glare from the following vehicle. Furthermore, the mirror can easily be knocked out of alignment when it is being operated. Also, it is easy to forget to return the mirror to the normal position when the source of glare has gone. According to the present invention, there is provided a mirror comprising a reflective surface and a transparent layer disposed over the reflective surface, the transparent layer being made from a photomorphic material whereby an increase in the intensity of light incident on the mirror results in an increase in the opacity of the transparent layer. With the mirror constructed in accordance with the present invention, the intensity of the reflected image varies in inverse proportion to the intensity of light incident on it. Thus, in normal night-driving conditions, the transparent layer would be substantially clear, but it would automatically become darker in response to the headlights of a following vehicle. The mirror may comprise simply a rigid sheet of photomorphic material, such as glass, of which one surface is silvered to provide the reflective surface. Alternatively, the mirror may comprise a sheet of clear glass of which one surface is silvered and the other surface is provided with a relatively thin layer of photomorphic material, such as glass or plastics material. It may thus be possible to convert existing mirrors by applying such a sheet to the front face. Thus, a further aspect of the present invention provides a method of modifying an existing mirror, the method comprising applying a layer of photomorphic material to the front face of the mirror. It will be appreciated that light incident on the mirror will pass through the transparent layer of photomorphic material twice, i.e. once on incidence and once on reflection. This means that the opacity of the transparent layer (dependent on the optical properties of the photomorphic material and on the thickness of the layer) does not have to be as great as would be required if the light were to pass only once through the transparent layer. Furthermore, if only a thin sheet of photomorphic material is used, it does not need to be of high optical quality. Although the present invention is primarily concerned with rearview mirrors for motor vehicles, mirrors in accordance with the present invention could be useful for other purposes, such as in remote welding or furnace viewing systems. For a better understanding of the present invention, and to show how it may be carried into effect, reference will now be made, by way of example, to the accompanying drawing, which shows a cross-section through a mirror. The mirror shown in the drawing comprises a clear glass sheet 2 which is provided with a layer of silvering 4 on one face so as to render that face reflective. The other face of the glass 2 is provided with a transparent layer 6 of photomorphic material whose opacity increases with increasing intensity of light falling upon it. The glass 2, with its two layers 4 and 6, is mounted in a support 8. In use of the mirror as the rear-view mirror in a motor car, the photomorphic layer 6 will become darker when, for instance, the headlights of a following vehicle shine upon it. This will reduce the glare of the headlights reflected from the mirror into the eyes of the driver. The photomorphic layer 6 may comprise a sheet which is loosely fitted to the front surtace or bonded thereto, or it may be sputtered or floated onto the surface of the glass 2. In order to avoid the effects of excessive darkening of the photomorphic layer 6 during normal daylight conditions, it may be desirable for this layer 6 to be removable from the face of the glass 2. Thus, the layer 6 may comprise a screen which is hinged to the rest of the mirror so that it can be pivoted out of the way when not required, for example when driving in daylight. The screen could then be hinged in front of the mirror only when driving at night. Claims

6. A mirror as claimed in claim 5, in which the layer of photochromic material is hinged with respect to the layer of non-photochromic material for movement between the use and nonuse positions.

7. A mirror as claimed in claim 1, in which the transparent layer of photochromic material is a substantially rigid sheet which is silvered on one face to provide the reflective surface.

8. A mirror substantially as described herein with reference to, and as shown in, the accompanying drawing.

9. A mirror as claimed in any one of the preceding claims, which is a rear-view mirror for a motor vehicle.

10. A method of modifying an existing mirror, comprising applying a layer of photochromic material to the front face of the mirror.