GB2047870A

GB2047870A - Signal Lamp Emitting Coloured Light

Info

Publication number: GB2047870A
Application number: GB8007493A
Authority: GB
Original assignee: Westfaelische Metall Industrie KG Hueck and Co
Current assignee: Westfaelische Metall Industrie KG Hueck and Co
Priority date: 1979-03-05
Filing date: 1980-03-05
Publication date: 1980-12-03
Also published as: FR2450996B1; DE2908453A1; IT8067333A0; GB2047870B; DE2908453C2; AU534513B2; FR2450996A1; IT1193407B; AU5563680A

Abstract

A signal lamp, for example for a vehicle, emitting coloured light has, in front of an incandescent lamp (3), a colour filter (7) with a spherical-cap-shaped central region adjacent the incandescent lamp. An optical disc (10) acting as a collecting lens and a cover disc (1) acting as a dispersion lens are disposed in succession in front of the colour filter. To minimise apparent false signals from external light escaping after reflection through the colour filter, the optical disc has an outwardly domed or conical central region into which the colour filter projects little if at all, and refractive prism elements (14) of the collecting lens are formed on the outer face of the domed region. The optical disc has at least one plane surface (11) provided with total-reflection prism elements (13) on its rear face. <IMAGE>

Description

SPECIFICATION Signal Lamp Emitting Coloured Light The invention relates to a signal lamp, particularly but not necessarily exclusively for vehicles, that is arranged to emit coloured light.

Such as for direction indicators, brake lights and so on.

Such lamps are known in which the disposition of a colour filter behind one or two clear cover discs that as a rule comprise the optical means for achieving the desired light distribution, serves both technical and aesthetic purposes. Often, the signalling colour of the lamps does not harmonize with the colour of the vehicle or gives an annoying colour contrast, particularly if the lamp is arranged inside of or next to the headlamps. In addition, use of a colour filter arranged behind clear cover discs is intended to make the lamp proof against external light, that is to say, the lamp should not create the impression that it is switched on when external light falls on it, particularly with sunlight with a shallow angle of incidence.

However, both of these objects are achieved only to a limited extent by the known signal lamps of this kind since light rays entering the lamp at an oblique angle may be deflected, for example by the front cover disc and by an inner optical disc behind it in such a manner that they hit the opposite side of that optical disc, through the colour filter, and are deflected by it in such a manner that they re-emerge from the lamp. Since these light rays pass through the colour filter, the lamp appears lit in the signalling colour, at least in partareas of the cover disc.

According to the present invention, there is provided a signal lamp, for example for vehicles, comprising, arranged in succession to each other in front of an incandescent lamp, a colour filter disposed adjacent to the lamp and having a convex cap-like form at least in its region closest to the lamp, an optical disc in front of the colour filter said optical disc having a domed region with refractive prism elements that form a collecting lens for light from the lamp, and at least one outer region comprising a plane surface with totalreflection prism elements, and a cover disc in front of the optical disc providing a dispersion lens for the lamp.

Preferably, on said optical disc the refractive prism elements are arranged on the outer face and the total-reflective prism elements on the inner face.

It is also advantageous if the distance between the colour filter and the optical disc is great enough for the colour filter not to project, or to project only insignificantly, past the plane into the domed area.

By constructing the outer regions of the optical disc as a plane surface, the light entering the lamp and penetrating this part of the optical disc cannot be refracted in such a manner that it reemerges from the lamp through the optical disc.

Instead, it can be absorbed by the interior of the lamp. Due to the use of refractive prism elements in the inner region of the optical disc and of totalreflection prisms in the outer region, the light incident on the optical disc is utilized optimally.

Arranging the refractive prism elements on the outer face of the optical disc has the advantage that the whole of the light hitting this area is deflected since the refractive prism elements arranged in this manner do not have any shaded areas. Arranging the refractive prism elements on a domed optical disc makes it possible to enlarge the area in which high-efficiency refractive prisms can be located. Compared to total-reflection prisms, refractive prisms have a higher efficiency since the former have one less reflecting surface.

It is more advantageous to arrange the refractive prism elements on a surface placed at an acute angle to the optical axis since this keeps the angle small between the light rays emerging from the incandescent lamp incident the prism elements and the perpendicular to the target surface. This produces less surface reflection at the targer surface of the beam. For the light rays penetrating into the lamp from the exterior, the above-mentioned angle is greater so that here a greater surface reflection is produced. In addition, the refractive prism elements provided on an outwardly directed domed area provide a greater proportion of surfaces at which the light entering from the exterior is totally reflected.

In an advantageous further development of the invention, that prism element which is nearest to the incandescent lamp, of the total-reflection prism elements provided on the plane outer region, is constructed in such a manner that the light incident on the optical disc from the exterior is reflected by total reflection. This prevents the external light incident on this prism element from being refracted in such a manner that it hits the opposite prism element, through the colour filter, to emerge from there as a false colour signal from the lamp.

In addition, it is of advantage if the inside wall of the lamp between the inner optical disc and the outer cover disc is bright, preferably silvercoloured, and the inside wall behind the inner optical disc is dark, preferably black. Such an arrangement has the advantage that the light hitting said wall between the optical discs is largely reflected, and the interior of the lamp thus appears to be bright, whereas the light penetrating the inner optical disc is absorbed and thus is not able to emerge from the lamp after passing through the colour filter.

The invention will be described in more detail by way of example with reference to the accompanying drawings, in which: Fig. 1 shows a vertical axial section, of a known lamp construction, and Fig. 2 shows a vertical axial section of a lamp according to the present invention.

The known lamp shown in Fig. 1 is provided with a clear colourless cover disc 1 comprising a dispersion lens 2. In the path of the light 4 emerging from incandescent lamp 3, the cover disc 1 is preceded by a clear colourless optical disc 5, the inside of which is formed with annular prism elements 6 acting as a collecting lens. This optical disc is outwardly domed so that it receives as large a share of the light emerging from the incandescent lamp 3 as possible and aligns it into parallel rays. The shorter the focal length of the prism elements 6 the closer the optical disc 5 can be placed to the incandescent lamp and the greater the solid angle of the light pattern picked up by the optical disc 5. Between the optical disc 5 and the incandescent lamp 3 a colour filter 7 is arranged which gives the light emerging from the incandescent lamp its signalling colour.The distance between the colour filter 7 and the incandescent lamp 3 must not be too small since otherwise localised heating occurs. However, because the optical disc must be placed as close as possible to the incandescent lamp and the distance of the colour filter 7 to the incandescent lamp 3 must not be too small, the distance between the colour filter 7 and the optical disc 5 is, of necessity, small. Since the optical disc 5 has a shape like a spherical cap, any light 8 from the exterior which hits the optical disc 5 towards one side, particularly obliquely, is deflected in such a manner that it is transmitted onto the prism elements 6 arranged on the opposite side, through the colour filter, and is aligned by them in such a manner that it emerges from the lamp as a signalling beam 9.Light entering from the outside and refracted in the manner shown by the rays 8 and 9, is thus caused by the lamp to appear in the signalling colour, despite the colourless nature of the discs 1 and 5.

In the lamp according to Fig. 2, the cover disc 1 also comprises a dispersion lens 2 and the colour filter 7 is also shaped like a spherical cap in an effective area. The interposed optical disc 10 is constructed to be domed outward only in its central region, the outer region 11 being constructed as plane areas. The inside faces of these plane areas 11 are formed with total reflection prism elements 13 which align the light 12 hitting them to be parallel or essentially parallel. In the outwardly domed central region of the optical disc 10 refractive prism elements 14 are arranged on the outer face which align the light 1 5 hitting them to be parallel or at least approximately parallel.These refractive collecting prism elements should have as short a focal length as possible so that light emitted from the lamp is picked up by the disc over a large solid angle.

The central region of the optical disc 10 is domed conically. Positioning the incident face 1 6 of the light in this manner has the advantage that the angle formed between the light beam 1 5 and the perpendicular to the region 1 6 is small and thus the proportion of light reflected by this region is also small.

The light 17, hitting the region 11 and the refractive prism elements 14 from the outside, is partially reflected at the surface and re-emerges directly through the cover disc 1. The light passing through the refractive prism elements 14 and total-reflection prism elements 13 passes through the filter disc 7 and is absorbed by blackened inner surface 18 of the lamp housing 1 9. Since the total-reflection prism elements 13 are provided on a plane area the rays deflected by these prism elements cannot impinge on another part of the optical disc 10. So that this similarly applies to prism element 20, located on the inside of the plane area 11, said element is constructed like a reflector prism whereby all of the light 21 falling on this prism from the exterior is reflected back to the exterior.This prevents the light hitting the prism element 20 from the outside from being directed through the filter disc 7 to the opposite prism element 20a and emerging from here as a false signal beam from the lamp. The same applies also to the light rays hitting the prism element 20a from the outside.

The distance between the colour filter 7 and the outwardly domed inner area of the optical disc 10 has been selected to be such that the colour filter 7 does not project, or only insignificantly so, past the plane surface 11 into the domed region of the optical disc 10. This prevents the light, refracted or reflected by the refractive prism elements 14 and hitting the opposite inside surface of the region 1 6 from first passing through the colour filter.

If the lamp is of a narrow and high construction, the plane areas can be omitted in the two opposite lateral regions.

It will thus be seen that by the measures described above, it is possible to so arrange the optical disc inside the lamp that as little as possible of the light entering the lamp from the exterior penetrates the optical disc, and that the proportion of the light penetrating the optical disc is absorbed to the greatest possible extent in the interior of the lamp or is reflected in such a manner that, if possible, only a small proportion passes back through the optical disc and that this small proportion of the light has not first passed through the colour filter.

Claims

1. A signal lamp, for example for vehicles, comprising, arranged in succession to each other in front of an incandescent lamp, a colour filter disposed adjacent to the lamp and having a convex cap-like form at least in its region closest to the lamp, an optical disc in front of the colour filter said optical disc having a domed region with refractive prism elements that form a collecting lens for light from the lamp, and at least one outer region comprising a plane surface with totalreflection prism elements, and a cover disc in front of the optical disc providing a dispersion lens for the lamp.

2. A signal lamp according to claim 1 wherein said total-reflection prism elements are arranged on the inside face of the optical disc.

3. A signal lamp according to claim 2, wherein of the total reflection prism elements, that element which is adjacent to the incandescent lamp is constructed in such a manner that all of the incident light from the exterior that it receives is reflected by total reflection.

4. A signal lamp according to any one of claims 1 to 3 wherein said refractive prism elements are arranged on the outside face of the optical disc.

5. A signal lamp according to any one of the preceding claims wherein the convex form of the colour filter is so arranged that it does not project, or projects only insignificantly past the plane of said plane surface of the optical disc.

6. A signal lamp according to any one of the preceding claims wherein an inside wall of the lamp between the cover and optical discs has a bright surface, preferably silver-coloured.

7. A signal lamp according to any one of the preceding claims wherein behind the optical disc the lamp has a dark, preferably black, inner wall surface.

8. A signal lamp, for example for vehicles, comprising an incandescent lamp having in succession in the path of light emitted by the lamp, a colour filter shaped at least in part like a convex cap, a colourless optical disc providing a collecting lens and outwardly domed, and a colourless cover disc providing a dispersion lens, and wherein: : a) the outwardly domed optical disc comprises a plane surface in its outer areas; b) said optical disc is provided with refractive prism elements in the domed area and with totalreflection prism elements in the area of the plane surface; c) the refractive prism elements are arranged on the outside of said disc and the total-reflection prism elements on the inside of said disc; d) the distance between the colour filter and the optical disc is great enough for the colour filter not to project, or to project only insignificantly, past the plane surface into the domed area.

9. A signal lamp constructed and arranged for use substantially as described herein with reference to Fig. 2 of the accompanying drawings.