Headlight

The headlight has a light ray guiding disk which is domed towards the source of light. This light ray guiding disk is structured as integral formed article and includes at its central zone, which has the smallest distance from the source of light, a collective lens structure. By means of this a substantial portion of the light rays emitted from the source of light into a spatial angle in front of the source can be focussed in the direction of the axis of the headlight. The light ray guiding disk can be manufactured as simple formed article. A transparent ring in a signal color is foreseen outside the light ray guiding disk. By means of this disk the stray light is utilized for a lateral marking when the headlight is used e.g. in a bicycle lighting arrangement.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a headlight for emitting light rays 
substantially along a headlight axis, which headlight has a source of 
light located on the headlight axis; a parabolic or elliptical reflector 
member; and a light ray guiding disk located in front of the source of 
light. This headlight is specifically suited as headlight for relatively 
low-power light sources such as for instance encountered at headlight 
apparatuses of bicycles. 
2. Description of the Prior Art 
In case of lighting devices, in which the supply power for the source of 
light is relatively weak, it is important that the generated light can be 
utilized in an optimal manner. As small as possible a portion thereof 
should get lost as stray light. Hereby it is to be differentiated between 
the light rays which travel from the source of light firstly onto the 
reflector member and which are reflected by same to extend approximately 
parallel, and those light rays which travel in a spatial angle from the 
source of light directly towards the light ray guiding disk. The first 
named, i.e. reflected light rays, can be rather easily deflected by the 
optics of the collective lens into the desired direction in order to 
produce a corresponding light cone. The light rays reaching the light ray 
guiding disk directly from the source of light pose the problem that the 
direction of the rays must be deflected relatively severely, for which 
task a collective lens must be present at the light ray guiding disk. This 
collective lens shall thereby cover as large as possible a spatial angle 
of the directly emitted light rays without, however, occupying a too large 
surface area of the light ray guiding disk. It has hereto already been 
suggested to bond a relatively thick collective lens to the inner side of 
the light ray guiding disk, which focuses the light rays coming directly 
from the source of light. This solution is, however, rather complicated 
and intrinsic regarding a manufacturing. 
SUMMARY OF THE INVENTION 
It is therefore a general object of the invention to provide a headlight 
which allows at an essentially unchanged expenditure regarding manufacture 
a substantially better utilization of the light rays coming directly from 
the source of light and allowing a reduction of stray light. 
A further object is to provide a headlight in which the light ray guiding 
disk is designed as an integral formed article having a domed section 
facing the source of light and comprising a collective lens structure 
formed thereinto at a central zone having a smallest distance from the 
source of light, whereby a substantial portion of the light rays emitted 
from the source of light at a spatial angle ahead of the source of light 
is focussed to extend at least approximately in the direction of the 
headlight axis. 
Because the light ray guiding disk is domed in the direction towards the 
source of light, a substantially larger spatial angle of the light rays 
stemming directly from the source of light can be utilized, whereby the 
collective lens structure, which is preferably designed as Fresnel lens, 
does not necessitate a substantial local thickening of the light ray 
guiding disk, which design does not lend itself to be controlled during 
the manufacture thereof. The light ray guiding disk designed in such a 
manner can for this reason be produced as integral shaped article of a 
plastic material or glass economically in accordance with common 
procedures. The stray light which is present in a reduced extent only is 
thereby utilized advantageously for the producing of a laterally visible 
illuminated zone at the headlight, for which task a transparent ring is 
formed at the periphery of the light ray guiding disk, through which zone 
the stray light exits radially.

Based on FIGS. 1 and 2 the optical structure of the headlight is initially 
explained basically prior to entering into further details. The headlight 
includes a source of light 1, which is preferably a halide lamp. In FIG. 1 
this source of light is designed as a point only, however in practice it 
is a spiral. The source of light is located in the focal point of a 
parabolic or elliptical reflector member 2. The light rays from the source 
of light which impinge onto the reflector member are, therefore, reflected 
roughly parallel to the axis 3 of the headlight and impinge in this manner 
onto the light ray guiding disk 4. The light ray guiding disk 4 is shaped 
of a material which is pervious to light rays, e.g. of a transparent 
plastic material, such as PMMA. Its shape and structure essentially 
determines the course of the light rays of the headlight. 
The light ray guiding disk 4 is divided into different zones. A central 
zone 5 is arranged for a deflection of the light rays coming directly from 
the source of light 1. The edge zones 6, 7, 8 located adjacent to the 
central zone 5 are divided into an upper zone 6, a middle zone 7 and a 
lower zone 8 (see FIG. 2) and operate for the deflection of the light rays 
which are reflected parallel by the reflector 2. 
The light ray guiding disk 4 is domed towards the source of light 1. This 
causes the central zone 5 to be located close to the source of light 1 
such that it may collect a relatively large spatial angle of the light 
rays received directly from the source of light 1. The light rays reaching 
the light ray guiding disk in the area of this spatial angle are collected 
by means of a collective lens structure to a light ray bundle 10, which is 
emitted substantially in the direction of the axis 3 of the headlight. 
In the central zone the structure of the collective lens is designed as a 
Fresnel lens 9, located concentrically to the axis 3, wherewith the 
thickness of the light ray guiding disk 4 remains roughly uniform. This is 
an important prerequisite for a manufacturing thereof as formed article 
made of a plastic material. Seen in the vertical section, the light ray 
guiding disk forms superimposed over this Fresnel lens a curve of the 
fourth order which causes the light rays extending at a higher area 
through this central zone 5 to be deflected somewhat stronger, i.e. 
towards the axis 3, than the rays extending at a lower area and which 
extend in the direction of the axis 3 (see FIG. 1). The result thereof in 
turn is that the cone of light which is obliquely incident on the roadway 
or another surface forms a light spot having a substantially constant 
brightness. In contrast to known headlights, the brightness in this light 
spot which is produced by the obliquely incident light cone, does not 
decrease at increasing distance from the headlight. 
A corresponding design of the light ray guiding disk is already present in 
the above mentioned edge zones 6, 7, 8, of which only the upper zone 6 and 
the lower zone 8 are visible in FIG. 1. Also here the light ray guiding 
disk forms when viewed in vertical section a curve in the fourth order 
additional to the circle leading to a corresponding stronger deflection of 
the light rays passing therethrough at a higher level. Accordingly, the 
light beams 11 and 12 emitted at these zones 6, 8 lead at an oblique 
incident also to a light spot at for example a supporting surface having a 
regular or uniform distribution of light. 
When viewing these zones in a horizontal section (see FIGS. 2 and 3), these 
zones have a dispersion lens structure 14 of a generally known kind, which 
leads according to FIG. 3 to a lateral diverging of the light cone. The 
edge zone 7 has the same design. 
If the headlight structured in the manner set forth above is used as 
bicycle headlight, it produces at a distance of 4 to 10 meters from the 
position of the headlight on the roadway a light spot of uniform 
brightness of an approximately trapezoidal shape. Because the direct light 
rays of the spatial angle extending through the central zone 5 add to the 
brightness, the utilization of light is substantially increased. 
FIG. 1 illustrates clearly that a part of the light rays from the source of 
light are neither reflected at the reflector member nor collected as 
direct light rays by the central zone. This stray light is now also 
utilized in that it exits laterally radially through a transparent ring 
15. This transparent ring has preferably a signal color such that when 
viewed from the side a band, shining in a signal color, is visible (see 
FIG. 4). In this way the stray light of the headlight adds to the lateral 
marking of for example a bicycle rider in the night, a state which 
otherwise is only possible by passive reflectors. This transparent ring 15 
at the same time can be structured as mounting member for the connection 
of reflector 2 and light ray guiding disk 4. 
FIG. 4 illustrates a possible embodiment of the described headlight as 
bicycle headlight. The headlight with its signal ring 15 and reflector 2 
is mounted at a housing 16. 
FIG. 5 illustrates, finally, a somewhat modified embodiment of the light 
ray guiding disk 4. According to the illustration, the difference between 
this embodiment and the embodiment of FIG. 1 is that the central zone 5 
forms itself once more a domed structure facing the source of light 1. By 
means of such a design it is made possible that the spatial angle of the 
direct light rays which is covered can be made still larger. 
FIG. 6 illustrates that the described headlight can additionally be 
equipped with a reflector ring 16 facing forwards. Should the source of 
light 1 or its power supply fail, this reflector ring 16 would allow a 
visibility of the bicycle for oncoming traffic in the night, in spite of 
such failure. The reflector ring 16 made of a transparent plexiglass has a 
reverse side 17 having a reflector structure. It is welded to a ring as 
signal ring 15 and made of a transparent red plexiglass, through which 
stray light can exit laterally in a manner disclosed above. The entire 
structure can be designed as snap-on ring for a mounting of the light ray 
guiding disk 4 at the reflector 2. In this embodiment the inventive 
headlight provides an integrated, actively and passively operating optical 
marking in traffic. 
In summarizing, the disclosed headlight allows to optimally utilize sources 
of light having a relatively low output for the generating of light, such 
as e.g. encountered in bicycle lighting devices, in that the losses due to 
light fog or stray light, respectively, are decreased and the light rays 
are emitted in an optimal manner in a directed state such that ahead of 
the bicycle a vast light spot, having a uniform distribution of light, is 
produced on the roadway. The components, specifically the light ray 
guiding disk, lend themselves to be manufactured by efficient methods as 
shaped or formed, respectively, articles. 
While there are shown and described present preferred embodiments of the 
invention, it is to be distinctly understood that the invention is not 
limited thereto, but may be otherwise variously embodied and practiced 
within the scope of the following claims.