EP0756131A1

EP0756131A1 - Vehicle lighting device

Info

Publication number: EP0756131A1
Application number: EP96112128A
Authority: EP
Inventors: Iordanka Neytcheva; Luciano Elia
Original assignee: Magneti Marelli SpA
Current assignee: Marelli Europe SpA
Priority date: 1995-07-28
Filing date: 1996-07-26
Publication date: 1997-01-29
Also published as: ITTO950640A1; ITTO950640A0; IT1280879B1

Abstract

A lighting device (1) presenting a light source (2); a reflector (3) housing the light source (2) at its focal point and presenting a front aperture (6); and a lens (4) covering the aperture (6) of the reflector (3). One face (4a, 4b) of the lens (4) presents a thin coating (7), which partially reflects the external and/or internal light rays incident on the lens (4) so as to conceal from the observer the inside of the lighting device (1), and which filters the light generated by the light source (2) so that the light transmitted outwards of the lighting device (1) is a different colour from that of the lens (4).

Description

The present invention relates to a vehicle lighting device, in particular a headlight or similar.
As is known, current vehicle lighting devices comprise a light source (bulb) for generating a light beam; a reflector having a reflecting surface which receives the light beam generated by the source and distributes it within a limited solid angle; and a transparent prismatic cover comprising a number of prismatic diffusing lenses which diffuse the light beam within a broader solid angle, in accordance with vehicle lighting regulations.
Conventional reflectors, which are in the form of a paraboloid and house the light source at the focal point, fail to provide for optimum distribution of the light, so that numerous design changes have been proposed to achieve the desired performance.
In particular, reflectors with complex nonparabolic reflecting surfaces comprising dissimilar portions joined in a variety of ways have been proposed to achieve the desired distribution of the luminous flux directly.
These surfaces do not require additional diffusers, and may be used with nonprismatic transparent covers comprising clear lenses.
Commercial application of clear lenses to vehicle lights, however, is currently hindered by the inside of the lighting device being visible, which may not always be acceptable aesthetically, and which is currently solved mechanically using concealing walls.
Moreover, increasing demand exists for outer lenses of a different colour from the light emitted, so that the chromatic effects of the lenses are more consistent with the look of the vehicle - while at the same time conforming with regulations governing the light emitted. This is currently achieved using high-contrast lenses which filter the light emitted by the lighting device.
The above solutions, however, involve fairly high-cost construction features, such as concealing walls and high-contrast lenses, which it would be preferable to dispense with.
The object of the present invention is therefore to provide a vehicle lighting device, particularly a headlight or similar, designed to overcome the aforementioned drawbacks.
According to the present invention, there is provided a vehicle lighting device, in particular a headlight or similar, comprising a light source for generating a light beam; a reflector having a reflecting surface and an aperture; and at least one lens for covering said aperture and distributing said light beam in space; characterized by comprising a coating on at least one face of said cover lens and/or on said reflecting surface; said coating at least partially reflecting and/or absorbing external and/or internal light rays incident on the coating.
A number of preferred non-limiting embodiments of the present invention will be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a horizontal section of a first embodiment of the device according to the invention;
Figure 2 shows a horizontal section of a variation of Figure 1.

Number 1 in Figure 1 indicates a lighting device comprising a light source (bulb) 2; and a reflector 3 presenting a parabolic or complex reflecting surface 3a, housing light source 2 at its focal point, and defining an aperture 6 covered by a clear lens 4.
The outer face 4b of lens 4 presents a coating 5 for at least partially reflecting and/or absorbing the light rays incident on it.
In the Figure 1 example, coating 5 comprises a thin film of dielectric material, metal or metal oxide.
For example, possible metals include aluminium and chromium; possible oxides include aluminium and chromium oxide; and possible dielectric materials include germanium oxide, silicon oxide and zinc sulphide.
These materials are deposited on lens 4 using known vacuum, sputtering or other processes not described in detail.
In the Figure 1 embodiment, coating 5 comprises a single layer, and acts as a semitransparent mirror for reflecting and/or absorbing some of the external light rays directed inwards of lighting device 1 and some of the internal light rays generated by light source 2 and directed outwards of lighting device 1.
More specifically, even in the event of low external reflectivity of coating 5 (about 10-20%), this has proved sufficient to conceal reflecting surface 3a of reflector 3 and light source 2, so that, from the outside, lighting device 1 is made nontransparent by an optical as opposed to a mechanical solution.
On the other hand, when light source 2 is on, the light generated by it travels through coating 5, the transmission and/or reflection and/or absorption percentage of which may be determined as required according to the material and the thickness of coating 5.
Figure 2 shows a variation of lighting device 1, wherein the coating, here indicated by 7, is formed on the inner surface 4a of lens 4, and comprises a number of layers 8 of different refraction indexes and a thickness of the order of the wavelength of the incident light.
Coating 7 in this case provides for two functions: on the one hand, it acts as a semitransparent mirror, as described with reference to Figure 1, to conceal the inside of device 1 when viewed from the outside; and, on the other, it acts as a selective interferential filter for filtering the light transmitted and/or reflected and/or absorbed externally of device 1, i.e. presents different reflection, transmission and absorption indexes for the different wavelengths of the incident light.
This is due to part of the incident light being reflected and/or transmitted and/or absorbed at the boundary between adjacent layers. More specifically, if the thickness of each layer 8 is an even whole multiple of half the wavelength of the light, constructive interference exists between the incident and reflected light and the total intensity of the light beam increases. Conversely, if the thickness of the dielectric is not a whole multiple of half the wavelength of the light, destructive interference exists and the total intensity of the light beam is reduced, even to the extent of being suppressed entirely if the thickness of the dielectric is an odd whole multiple of half the wavelength of the light.
This therefore provides, in the case of white incident light, for reflecting a monochromic colour, e.g. blue, or a composite colour, e.g. cyan, and for transmitting the rest of the spectrum, e.g. yellow in the first case and red in the second, thus enabling a wide variety of colours of the headlight, depending on the thickness of layers 8 of coating 7.
In both the above embodiments, coating 5 or 7 is preferably only reflective and/or absorbent and/or transparent for a given range of wavelengths, or is nonreflective for all or a given range of wavelengths.
The advantages of the lighting device according to the present invention are as follows. Coating 5 or 7 is deposited relatively easily and provides for optically as opposed to mechanically masking the inside of the headlight, thus reducing cost by eliminating the concealing walls.
Moreover, by virtue of the selective characteristics of the coating, the headlight may differ in colour from the externally visible light, thus conforming with regulations governing the colour of the emitted light, while at the same time satisfying increasing demand for special colour designs, and also enabling saving by eliminating the use of expensive high-contrast lenses.
Clearly, changes may be made to the lighting device as described and illustrated herein without, however, departing from the scope of the present invention.
In particular, coating 5 or 7 may be deposited indifferently on inner face 4a or outer face 4b of lens 4, or on reflecting surface 3a of reflector 3.
Whether the single-layer (coating 5) or multilayer (coating 7) solution is used depends on the desired colour characteristics, so that the multilayer solution (coating 7) may also be applied to the outer face of lens 4 or to reflecting surface 3a, and the single-layer solution (coating 5) may also be applied to the inner face 4a of lens 4 or to reflecting surface 3a.

Claims

A vehicle lighting device (1), in particular a headlight or similar, comprising a light source (2) for generating a light beam; a reflector (3) having a reflecting surface (3a) and an aperture (6); and at least one lens (4) for covering said aperture (6) and distributing said light beam in space; characterized by comprising a coating (5; 7) on at least one face (4a, 4b) of said cover lens (4) and/or on said reflecting surface (3a); said coating (5; 7) at least partially reflecting and/or absorbing external and/or internal light rays incident on the coating.
A lighting device as claimed in Claim 1, characterized in that said lens (4) comprises a first (4a) and second (4b) face opposite each other, said first face (4a) facing said light source (2); and in that said coating (7) is applied to said first face (4a).
A lighting device as claimed in Claim 1, characterized in that said lens (4) comprises a first (4a) and second (4b) face opposite each other, said first face (4a) facing said light source (2); and in that said coating (5) is applied to said second face (4b).
A lighting device as claimed in any one of the foregoing Claims, characterized in that said coating (5; 7) is reflective and/or absorbent and/or transparent for a given range of wavelengths.
A lighting device as claimed in any one of the foregoing Claims from 1 to 3, characterized in that said coating (5; 7) is nonreflective for at least a given range of wavelengths.
A lighting device as claimed in any one of the foregoing Claims, characterized in that said coating (5) comprises one layer.
A lighting device as claimed in Claim 6, characterized in that said coating (5) is made of a material selected from the group comprising metals, metal oxides and dielectric materials.
A lighting device as claimed in any one of the foregoing Claims from 1 to 5, characterized in that said coating (7) comprises a number of layers (8).
A lighting device as claimed in Claim 8, characterized in that pairs of adjacent layers (8) present different refraction indexes for different wavelengths; and in that each said layer (8) is made of a material selected from the group comprising metals, metal oxides and dielectric materials.
A lighting device as claimed in Claim 7 or 9, characterized in that said material is selected from the group comprising aluminium, chromium, aluminium oxide, chromium oxide, zinc sulphide, germanium oxide and silicon oxide.