Headlight for vehicle in accordance with projection principle

A headlight for a vehicle operating in accordance with the projection principle, the headlight has a reflector, a light source, a lens through which a light reflected by the reflector passes, at least one partially light-permeable element which surrounds the lens at least over a part of its periphery, so that light which is emitted by the light source and not engaged by the reflector passes through and is collected by the at least one element, wherein, the reflector and the lens being formed so that light which is reflected by the reflector and passes through the lens forms an upper bright-dark limit, the element being formed at least locally as a fresnel lens with ring-shaped optical profiles, and further optical profiles arranged at least in a part of a beam path of the light passing through the element and deviating the light so that it illuminates a region in front of the vehicle above the bright-dark limit formed by the light reflected by the reflector and passing through the lens.

BACKGROUND OF THE INVENTION 
The present invention relates to a headlight for vehicle, which operates in 
accordance with a projection principle. 
Headlights of the above mentioned general type are known in the art. One of 
such headlights is disclosed for example in the German patent document DE 
32 18 703 A1. This headlight has a reflector, a light source and a lens 
through which the light reflected by the reflector passes. Moreover, the 
headlight has a light-permeable element which surrounds the lens at least 
over a part of its periphery. The light emitted by the light source which 
is not engaged by the reflector can pass through the light-permeable 
element and be collected. For this purpose the element has prisms for 
deviating the passing light. With this construction of the element, when 
the light source is turned on, the illuminated surface of the reflector is 
increased relative to the surface of the lens, so that by the headlight no 
or only a small subjective screening is caused. The light bundle which is 
reflected by the reflector and passes through the lens has a sharp 
bright-dark limit which is advantageous for avoiding a blinding of a 
counter traffic, but on the other hand has the disadvantage that high 
ranged objects such as for example traffic screens or direction screens 
are not illuminated or illuminated insufficiently and therefore are 
difficult to recognize by the vehicle driver. Also, only a part of the 
light passing through the element can be engaged by the prisms of the 
element. The known headlight also has the disadvantage that when the light 
source is turned off, the element is perceived as dark and the headlight 
has an undesired, non uniform appearance image. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide a 
headlight for a vehicle operating in accordance with the projection 
principle which avoids the disadvantages of the prior art. 
In keeping with these objects and with others which will become apparent 
hereinafter, one feature of present invention resides, briefly stated, in 
a headlight for a vehicle, in which the element at least partially is 
formed as a fresnel lens with ring-shaped optical profiles, and at least 
in a part of a beam path of the light passing through the element has 
further optical profiles which deviate the light so that it illuminates a 
region in front of the vehicle above the bright-dark limit of the light 
reflected by said reflector and passing through said lens. 
When the headlight is designed in accordance with the present invention, 
with the element formed as fresnel lenses, the light emitted by the light 
source during passage through the element can be collected with a high 
efficiency. Due to the optical profiles of the disk, the light passing 
through the element also is deviated so that a sufficient illumination 
above the bright-dark limit is provided. 
In accordance with another feature of the present invention, the further 
optical profiles are arranged on a light-permeable disk which is located 
in a light outlet direction after the element, and the disk is formed as a 
cover disk of the headlight. 
In accordance with still a further feature of present invention, at least 
partially reflecting layer is arranged in the beam path of the light 
passing through the element, at least locally, facing in the light outlet 
direction. With the at least partially reflecting layer in the turned-off 
condition of the headlight a brilliant appearance is provided. Due to the 
collecting action of the fresnel lenses, despite the partial screening of 
the light passing through the element by the layer, still a sufficient 
illumination of the region around the lens is provided. 
The novel features which are considered as characteristic for the present 
invention are set forth in particular in the appended claims. The 
invention itself, however, both as to its construction and its method of 
operation, together with additional objects and advantages thereof, will 
be best understood from the following description of specific embodiments 
when read in connection with the accompanying drawings.

DESCRIPTION OF PREFERRED EMBODIMENTS 
A headlight as shown in FIGS. 1-4 is provided for a vehicle, in particular 
a motor vehicle. It operates in accordance with a projection principle and 
serves for producing at least a dim light. The headlight has a reflector 
10 which is composed of a synthetic plastic or metal, and a light source 
12 inserted in an apex region of the reflector. The light source 12 can be 
an incandescent lamp, a gas discharge lamp, or another suitable lamp. A 
lens 16 composed of glass or synthetic plastic is arranged after the 
reflector 10 as considered in the light outlet direction 14. The lens 16 
can have for example a plane side 18 which faces the reflector 10 and an 
opposite convex curved side 20. 
The lens 16 is held in a supporting element 22 which can be connected with 
a front edge 22 of the reflector 10, which faces in the light outlet 
direction 14. The reflector 10 and the lens 16 can be accommodated in a 
housing 15 which has a light outlet opening covered with a light-permeable 
disk 17 of glass or synthetic plastic. The cover disk 17 can be smooth, so 
that light can pass through it without being changed. Alternatively, it 
can be provided at least partially with optical elements, which deviate 
the passing light, for example disperses the light. 
The light emitted by the light source 12 is reflected by the reflector 10 
as a converging light bundle which passes through the lens 16 and is 
deviated. The lens 16 acts as a collecting lens. The light passing through 
it is refracted to the optical axis 11 of the reflector 10. The reflector 
10 can have at least approximately ellipsoidal shape, and ellipsoid-like 
shape, or a numerically determined shape which is produced from the 
characteristic of the light bundle reflected by the reflector 10. 
A light-impermeable screen 26 is provided between the reflector 10 and the 
lens 16. It is arranged substantially under the optical axis 11. Only a 
part of the light bundle reflected by the reflector 10 can pass on it. The 
light bundle passing the screen 26 contains a bright-dark limit which is 
determined by the upper edge of the screen 26. It is formed by the lens 16 
as the bright-dark limit of the dim light bundle exiting the headlight. 
Alternatively, the screen 26 can be dispensed with when the shape of the 
reflector 10 is formed so that the light bundle reflected by the reflector 
already has the required bright-dark limit which is formed by the lens 16. 
The reflector 10 at its front edge 24 has a cross-section Q1, and the lens 
16 has a cross-section Q2 which is smaller than the cross-section Q1. The 
supporting element 22 can be provided with one or several webs 28. They 
extend from the front edge 24 of the reflector 10 close to the lens 16, 
where they can be connected with one another for example by a ring-shaped 
portion 30 in which the lens 16 is held with its edge. The light emitted 
by the light source 12 and not engaged by the reflector 10 can pass 
through openings 32 which remain between the webs 28. 
The webs 28 are maintained preferably as small as possible to provide large 
openings 32 between them, so that a corresponding great part of the light 
emitted by the light source 10 can pass through them. Alternatively, the 
supporting element 22 can be also composed of at least partially 
light-permeable material, for example synthetic plastic or glass. In this 
case, the supporting element 22 does not have to provided with any 
openings. 
The headlight further has at least one element 40 which surrounds the lens 
16 over at least a part of its periphery. FIGS. 1 and 2 show the first 
embodiment of the headlight. The element 40 surrounds the lens 16 over its 
whole periphery and is composed of a light-permeable material, such as for 
example glass or synthetic plastic. The lens 16 and the element 40 can be 
of one-piece with one another. The element 40 at least locally, but 
preferably over its total extension, is formed as a fresnel lens and has a 
plurality of concentric, ring-shaped optically active profiles 42. The 
optical profiles 42 are arranged at the side of the element 40 which faces 
the reflector 10 opposite to the light-outlet direction 14. 
The optical profiles 40 are formed for example wedge-shaped. They deviate 
the light passing through the element 40 toward the optical axis 11 and 
thereby collect the light. The optical profiles 42 can be formed for 
example so that the light emitted by the light source 12 after passage 
through them extends substantially parallel to the optical axis 11. The 
element 40 can be arranged as shown in FIG. 1 so that in direction of the 
optical axis 11 it has substantially the same distance from the reflector 
10 as the lens 16. Alternatively, the element 40 can have in direction of 
the optical axis 11 also another distance from the reflector 10 as the 
lens 16 and therefore offset to the lens 16. 
The element 40 has an opening 41 for passage of the lens 16. In the first 
embodiment shown in FIG. 1, the element 40 is substantially flat. 
Alternatively, the element 40 can be for example convex or concave with a 
corresponding curvature. The element 40 has for example a round shape as 
shown in FIG. 2. The shape of the element 40 can be selected arbitrarily, 
for example also oval or cornered, depending on what appearance of the 
headlight is desired. It can be provided that the element 40 surrounds the 
lens 16 only over a part of its periphery, and for example is arranged 
laterally near the lens 16 or above and/below the lens 16. 
At its side facing in the light outlet direction 14, the element 40 is 
provided at least locally with further optical profiles 44 which deviate 
the passing light. The further optical profiles 44 of the element 40 are 
formed so that the light passing through it is deviated upwardly and forms 
a light bundle extending above the bright-dark limit of the light bundle 
reflected by the reflector 10 and passing through the lens 16 on the 
screen 26. The further optical profiles 44, as shown in FIG. 2, can be 
formed as substantially horizontally extending lenses which disperse light 
at one side upwardly. 
FIG. 5 shows a measuring screen 80 which is arranged at a distance from the 
headlight and is illuminated by the light emitted by the headlight. The 
horizontal central plane of the measuring screen 80 is identified with HH, 
while the vertical central plane is identified with VV. The horizontal 
central plane HH and the vertical central plane VV intersect each other in 
a point HV. The light reflected by the reflector 10 and passing on the 
screen 26 through the lens 16 illuminates the measuring screen 80 in a 
region 82. The region 82 is limited upwardly by the bright-dark limit 
produced by the screen 26. In the shown embodiment, the reflector is 
formed for a right traffic and the bright-dark limit has a horizontally 
extending portion 84 at the counter traffic side or in other words at the 
left side of the measuring screen 80 under the horizontal central plane 
HH. At the traffic side, or in other words, at the right side of the 
measuring screen 80, the bright-dark limit has a portion 86 which extends 
from the horizontal portion to the right edge of the measuring screen 80 
till above the horizontal central plane HH. Alternatively, the bright-dark 
limit can also have a substantially horizontal portion at the traffic 
side, which is arranged higher than the horizontal portion 84 of the 
counter traffic side. The distribution of the illumination intensities in 
the region 82 is provided by legal considerations, wherein in a zone above 
the point HV the highest illumination intensity are available. Above the 
bright-dark limit 84, 86, the measuring screen 80 is not illuminated or 
illuminated only insignificantly by the light bundle which is reflected by 
the reflector 10 and passes on the screen 26 through the lens 16. 
The light which extends through the element 40 and is deviated upwardly by 
the further optical profiles 44 illuminates the measuring screen 80 in a 
region 88 arranged at a distance above the bright-dark limit 84, 86. The 
light passing through the element 40 acts in the region 88 to provide such 
an illumination, that the legal prescriptions are maintained over required 
average illumination intensities and maximum permissible highest 
illumination intensities. For example in the ECE regulations 20 which are 
accepted in Europe, a measuring point B 50 L is defined, in which the 
illumination intensity must amount maximum to 0.4 lux, to avoid blinding 
of the opposite traffic. With consideration of the legal prescriptions, 
the illumination intensity distribution in the region 88 can be freely 
selected. The illumination intensity distribution can be for example 
selected so that the region 90 of the measuring screen 80 located directly 
above the bright-dark limit 84, 86, which extends for example up to 
approximately 2.degree. above the horizontal central plane HH and under 
substantially 4.degree. at opposite sides of the vertical central plane 
88, is illuminated only weakly by the light passing through the element 
40. The region 88 which adjoins upwardly and laterally the region 90 
extends for example vertically upwardly up to approximately 4.degree. over 
the horizontal central plane HH and laterally at both sides of the 
vertical central plane W substantially up to 80 and is illuminated 
stronger than the region 90. 
In accordance with a further embodiment of the inventive headlight, the 
side of the element 40 which faces the light outlet direction 14 can be 
provided at least locally with at least partially reflective coating 46. 
The coating 46 can be formed so that it is light-impermeable. Then it is 
arranged only locally on the element 40, to make possible a partial 
passage of the light emitted by the light source 12. The coating 46 can be 
formed by lines or rings. The light impinging from outside of the coating 
46 is reflected by it. Alternatively, the coating 46 can be formed so that 
it is partially light-permeable and partially reflecting. In this case, 
the total surface of the element 40 can be covered by the coating 46, or 
only a part of its surface. The light emitted by the light source 12 can 
partially pass through the coating 46, so that it illuminates the region 
88 of the measuring screen 80, while the light impinging from outside of 
the coating 46 is partially reflected. 
The coating 46 can be composed preferably of metal, such as aluminum and 
can be applied by known methods on the element 40, for example by 
evaporation, sputtering, varnishing, printing or impregnating. The light 
permeability of the coating 46 can be varied by its thickness, and the 
light permeability reduces with increasing thickness. In order to provide 
a partial light permeability of the coating 46, it can have a small 
thickness, while for obtaining a high reflection degree, it can be 
provided with a correspodingly greater thickness. The coating 44 can be 
applied for example on the surfaces of the further optical profiles 44 of 
the element 40 which face in the light outlet direction 14. 
FIG. 3 shows the headlight in accordance with a second embodiment of the 
present invention in a section. The basic construction of the headlight 
with the reflector 10, light source 12, lens 16 and screen 26 is the same 
as in the first embodiment. The headlight in accordance with a second 
embodiment has an element 50 which surrounds the lens 16 at least over a 
part of its periphery and is also formed as a fresnel lens. It has the 
ring-shaped concentric optical profiles 52 which can be arranged on the 
side facing away of the light outlet direction 14 or facing in the light 
outlet direction 14 of the element 50. The element 50 has only the optical 
profiles 52 for forming a fresnel lens, while the other side of the 
element 50 is smooth. A light-permeable disk 53 is arranged after the 
element 50 in the light outlet direction 14. It extends at least over a 
part of the beam path of the light extending through the element 50. The 
disk 53 is provided at least locally with optical profiles 54. In their 
action they correspond to the further optical profiles 44 of the element 
40 of the first embodiment. They deviate the light passing through the 
element 50, so that it illuminates the measuring screen 80 as explained 
above, in the region 88. 
The optical profiles 54 can be arranged at the side of the disk 53 which 
faces opposite to the light outlet direction 14 or in the light outlet 
direction 14. The disk 53 can be formed substantially flat, or convex or 
concave with any curvature. At the side of the disk 53 which faces in the 
light outlet direction 14, a coating 56 is applied, which is, formed and 
arranged as the above described coating 46 of the element 40. The disk 53 
can be provided in its central region with an opening 54. The light 
passing through the lens 60 can pass through the opening 57 without 
problems. Alternatively, the disk 53 can also extend over the beam path of 
the light passing through the lens 16. Then the disk 53 in the region of 
the beam path of the light passing through the lens 16 has no optical 
profiles 54 to provide an unimpeded passage of this light. 
FIG. 4 shows a third embodiment of the headlight in accordance with the 
present invention in a section, in which the basic construction of the 
headlight with the reflector 10, the light source 12, the lens 16 and the 
screen 26 corresponds to that of the first embodiment. An element 60 
surrounds the lens 16 at least over a part of its periphery and is formed 
as a fresnel lens. It has a ring-shaped, concentric optical profile 62 
which can be arranged at the side of the element 60 facing opposite to the 
light outlet direction 14 or in the light outlet direction 14. The element 
60 has only the optical profiles 62 for forming a fresnel lens, while the 
other side of the element 60 can be formed smooth. 
At least in a part of the beam path of the light separated by the element 
60, optical profiles 64 are arranged. They deviate upwardly the light 
passing through, so that it illuminates the region 88 of the measuring 
screen 80 of FIG. 5. The optical profiles 64 in accordance with a third 
embodiment of the invention are arranged on the cover disk. 17, preferably 
at its inner side facing opposite to the light outlet direction 14. The 
cover disk 17 has the optical profiles 64 only in a region, through which 
no light reflected by the reflector 10 and separated on the screen 26 by 
the lens 16 can pass. The cover disk 17 has the region through which the 
light passes which is reflected by the reflector 10 and separated on the 
screen 26 by the lens 16. This region of the cover disk 17 can be smooth 
or can be provided with optical profiles which are formed differently from 
the optical profiles 64. The element 60 can be provided at its side facing 
the light outlet direction 14 with at least partially reflecting coating 
66. With respect to its design and arrangement, it is similar to the 
coating 46 described in the first embodiment. The coating 66 can be also 
arranged on a disk provided between the element 60 and the cover disk 17, 
at its side facing the light outlet direction 14. 
It will be understood that each of the elements described above, or two or 
more together, may also find a useful application in other types of 
constructions differing from the types described above. 
While the invention has been illustrated and described as embodied in 
headlight for vehicle in accordance with projection principle, it is not 
intended to be limited to the details shown, since various modifications 
and structural changes may be made without departing in any way from the 
spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of this invention.