A METHOD PERTAINING TO VEHICLE HEADLAMPS WHICH EMIT ULTRAVIOLET-LIGHT, AND AN ARRANGEMENT HEREFOR

Abstract: A method pertaining to vehicle headlamps which emit ultraviolet light and which include a light source for generating both ultraviolet light and visible light, and a filter which is placed in the beam path between the light source and the surroundings and which is intended to substantially filter out visible light and to transmit ultraviolet light, said headlamp, however, unintentionally transmitting a given proportion of visible light, such as red and blue light, of low intensity. The invention is characterized by arranging the headlamp (1) so that the light source (2) and the filter (5; 6) in combination will intentionally allow a predetermined proportion of visible light of a light colour to pass therethrough; by causing said visible light to be sufficiently strong to dominate over said unintentionally emitted light on the part of a viewer, and by causing said predetermined proportion of visible light to have an intensity which lies beneath the intensity at which the light intentionally emitted would dazzle a viewer in combination with any other visible light intentionally emitted by the headlamp. The invention also relates to an arrangement.

Description: A Method Pertaining to Vehicle Headlamps Which Emit Ultraviolet Light, and an Arrangement Herefαr. The present invention relates to a method pertaining to vehicle headlamps vihich emit ultraviolet liφt, and to an arrangement herefor In recent times, great interest has been shown in the development of vehicle headlamps which emit light within the ultraviolet wavelength range. Lamps which emit ultraviolet light have the decisive advantag of enabling fluorescent objects to be seen by the driver of the vehicle. Swedish Patent Specification No. 8704118-2, among others, describes one such headlanp. This headlamp functions to emit both visible liφt and ultraviolet light. The headlamp is constructed to produce a full-beam lobe with ultraviolet light and a dipped beam lobe with visible light. It is previously kncwn to provide separate headlamps which emit essentially only ultraviolet liφt. Woods glass is an example of a filter that can be used to filter- out visible liφt. This filter, however, has the drawback of allowin a given proportion of red liφt and a given proportion of blue liφt to pass throuφ. Althσuφ the red and the blue liφt are weak, they are nevertheless found to be disturbing or disoαmfαrting to people who look into the headlamp which emits said liφt. Althouφ this effect is difficult to describe, it has been judged sufficiently significant to wish to reduce or to el__minate the same. The effect is much more noticeable with headlamps which emit essentially only ultraviolet liφt. One of the reasons for this effect is that red and blue liφt is diffracted by the human eye to different extents, which can be referred to the phenomenon of bichrcmatic alteration. This would give rise to the aforesaid feeling of discomfort. Attempts have been made to produce improved filters with well-defined lJ ts. It is very difficult to produce filters with well-defined liπiits, and it is also doubtful that this is the correct procedure t follow, since the sensitivity of the eye does not decrease with a sharp limit between different wavelengths. The difficulties ejcperienced by people who look into a vehicle headl which emits ultraviolet liφt are eliminated, or at least considerab reduced, by means of the present iπveπticxi. Ax_x_cdingly, the present invention relates to a method pertaining to vehicle headlamps which emit ultraviolet liφt and which include a liφt source far generating both ultraviolet liφt and visible liφt, and a filter whicii is placed in the beam path between the liφt source and the su__rcundings and which is ____ten__ed to substantially filter out visible liφt and to transmit ultraviolet liφt, said headlanp, however, un__ntentianally transmitting a given prcportiαn of visible liφt, such as red and blue liφt, of low intensity, said method being characterized by cxinstructing the headlanp so that the light source and the filter in combination will intentionally allow a predetermined proportion of visible liφt of a liφt colour to pass t__eret__r * αuφ; fcy causing said visible liφt to be sufficiently strong to dominate over said un__ntentionally emitted liφt on the part of a viewer, and by causing said predetermined proportion of visible liφt to have an intensity which lies beneath the intensity at which the liφt intentionally emitted would dazzle a viewer in combination with any other visible liφt intentionally emitted by the headlamp. The invention also relates to an arrangement of the kind set forth in the preamble of Claim 6 and having the ciiaracteristic features set forth in said Claim. The .Invention will now be described in more detail with reference to e επplifying embodiiπeπts thereof illustrated in the accαπpanying drawing, in which - Figure 1 illustrates a first exemplifying embodiment of the inven¬ tion; - Figure 2 illustrates a second exemplifying embodiment of the invention; - Figure 3 illustrates a third exemplifying eππibodiment of the invention; and - Figure 4 is a schematic, cross-sectional view of a headlanp and illustrates two different embodiments of the invention. Figure 4 illustrates a vehicle headlanp 1 which is intended to emit ultraviolet liφt. The headlanp 1 includes a liφt source 2 which functions to produce both ultraviolet liφt and visible liφt. The liφt source is preferably a mercury discharge lamp. A filter is provided in the beam path between the liφt source 2 and the surround ings 3, primarily in front of the headlanp glass 4. The filter is mainly intended to filter-out visible liφt and to emit ultraviolet liφt. The filter is arranged in two different ways in the Figure 4 illu¬ stration. One method of arranging the filter is to place the filter 5 inwardly of the headlamp glass 4, αr to incorporate the filter in the actual headlanp glass itself. Another method is to form the filter as a cylindrical cup 6 around the actual liφt source 2. Still another method is to integrate the filter with the lamp glass of the liφt source. In all of these alternative methods, the liφt emitted by the liφt source will be filtered so that the liφt emitte by the vehicle headlanp will be ultraviolet liφt. The filter may be comprised of Woods glass or seme other suitable filter material. It has been found that such headlamps, however, will also emit a given proportion of visible liφt, such as red or blue liφt of low intensity, despite the intention of filtering-cut all, or substantial all, visible liφt, so that a person gazing into the lamp will not ei erienσe the presence of visible liφt. According to the invention, the headlanp is constructed so that the liφt source and the filter are caused, in combination, to intention- ally allow a predetermined proportion of visible liφt of a liφt colour to pass thrαuφ, said visible liφt being given sufficient strength to dominate over the liφt that is unintentionally emitted, as experienced by a viewer, and to give said urtinteπtiαnal liφt an intensity which lies beneath the intensity at ch the __πtenticrølly emitted liφt would dazzle a viewer in combination with any other visible light intentionally emitted by the headlamp. __n this respect, it is not important where the filter is placed in the beam path of the headlamp such that a part of the liφt produced by the liφt source is emitted by the headlanp without having been filtered with regard to visible wavelengths. By any other intentionally-emitted visible liφt is meant liφt from other vehicle headlamps. Thus, according to one preferred embodiment of the invention, the liφt which is emitted intentionally is mainly yellow αr white liφt. Since discharge laπps of the aforesaid kind emit a hiφ proportion of white liφt, it is not necessary to filter the emission of liφt. In order to emit yellow liφt, or liφt of seme other colour, it is neσesary, of course, to filter the visible liφt to be emitted to the colour intended scι_ewhere in the beam path, so as to obtain liφt of the colour intended, in a known manner. It has surprisingly been found that the emission of a minor quantity of visible liφt of liφt colour and of an intensity such as not to dazzle a viewer is sufficient to fully dominate over the blue and red liφt. This eliminates the cause of the discomfort felt when looking into a conventional headlanp. The visible liφt is preferably emitted over a given area of the headlanp glass 4. According to one preferred embodiment, this surface area of the headlamp glass thrσuφ which visible liφt is intentionall emitted is about 0.02 to 5%, preferably about 0.2 to 2%. According to one preferred embodiment, the headlanp is constructed so that the iπtention__Uy-emitted visible liφt is caused to be emitted as an cuter frame 7 within which essentially solely ultraviole liφt is emitted. The frame 7 externals around the edge of the headlanp glass 4. ultraviolet liφt is thus emitted throuφ the remaining surface 8. This embodiment is illustrated in Figure l, which illu- strates a headlamp schematically frc the front. By the expression arranging the headlanp in the described manner is meant to construct the filter in combination with the liφt source in a manner to achieve said result. One skilled in this art will have no problem in σαr__ftι_uσting the headlamp in this way. One such method is to use a filter 5 according to Figure 4, in which visible liφt 13 is emitted at the edges of the filter 5, while ultraviolet liφt 14 is emitted over an area ∞rrespαrκling to the filter area. Figures 2 and 3 illustrate two alternative second preferred embodiment in which the headlanp is constructed such that the intentiαnally- emitted visible liφt is emitted at one point 9 or several points 10 over the surface of the headlanp glass where substantially solely ultraviolet liφt is emitted throuφ the remainder of the headlamp surface 11; 12. These points may be uniformly distributed over the surface of the headlamp glass and may be provided in a number such that the whole of the headlanp glass will appear to shine weakly in said liφt colours. It is obvious that the filter, in combination with the liφt source, can be given a large number of di ferent configurations with regard to the areas in which visible and ultraviolet liφt are emitted, and that Figures 1-3 merely illustrate examples of such configurations. The essential criterion is that sufficient visible liφt is emitted to dominate over the blue and red liφt so as to greatly reduce or eliminate the cause of discomfort mentioned in the introduction, at the same time as the emitted visible liφt will not dazzle a person observing the headlamp. Althouφ the invention has been described with reference to different exeπplifying embodiments thereof, it will be understood that these eπtoodjjceπts can be modified in many ways. For ejcample, the headlamp can be constructed to emit visible liφt of colours different to those before mentioned. Furthermore, other filters can be used. Neither is the present invention restricted to any particular headlan construction. The invention is therefore not restricted to the εtfαredescribed and illustrated embodiments, since modifications and variations can be made within the scope of the following Claims.

Claims: Claims 1. A method pertaining to vehicle headlamps which emit ultraviolet liφt and which include a liφt source for generating both ultraviol liφt and visible liφt, and a filter which is placed in the beam path between the liφt source and the su__rσundings and which is intended to substantially filter out visible liφt and to transmit ultraviolet liφt, said headlanp, however, iiniπtenticnally transmitti a given proportion of visible liφt, such as red and blue liφt, of low intensity, ch ar a cter i z ed by cαnstoictirig the headla (1) so that the liφt source (2) and the filter (5; 6) in cotobination will intentionally allow a prectetermined proportion of visible liφt of a liφt colour to pass therethrαuφ; by causing said visible liφt to be sufficiently strong to dominate over said imin entionally emitted liφt on the part of a viewer, and by causing said pre¬ determined propαrtion of visible liφt to have an intensity which lies beneath the intensity at which the liφt intentionally emitted would dazzle a viewer in combination with any other visible liφt intentionally emitted by the headlanp. 2. A method according to Claim l, cha r a c t e r i z e d in that the ir_πentionally-emitted liφt is substantially yellow or white liφt. 3. A method according to Claim lor 2, charac¬ ter i z ed by arranging the headlamp (1) so that the intention¬ ally-emitted visible liφt is emitted as an outer frame (7) within which substantially only ultraviolet liφt is emitted. 4. A method according to Claim 1, 2 or 3, charac¬ ter i z ed by σαnstruσting the headlanp (1) so that the intention ally-emitted visible liφt is emitted in one (9) or several (10) points over the surface of the headlanp glass (4) wherein substantial only ultraviolet liφt is emitted over the remaining surface area (11; 12) of the headlamp glass (4) . 5. A method according to any one of the preceding Claims, characterized in that the proportion of the surface of the headlanp glass (4) where visible liφt is intentionally emitted is about 0.02 to 5%, preferably about 0.2 to 2%. 6. An arrangement in vehicle headlamps which emit ultraviolet liφt, said headlamp including a liφt source for producing both ultraviolet liφt and visible liφt, and a filter placed in the beam path between the liφt source and the surroundings and constructed to essentially filter s -cut visible liφt and to transmit ultraviolet liφt, said headlanp, however, unintentionally emitting given visible liφt, such as red and blue liφt, of low intensity, cha r a c t e r i z e d in that the headlamp (1) is constructed so that the liφt source (2) and the filter (5; 6) in ccmbination will .intentionally allow a predetermined propαrtiαn of visible liφt of liφt colour to pass throuφ, said visible liφt being sufficiently strong to dominate over the unintentionally emitted liφt as experienced by a viewer, and to have an intensity which is beneath the intensity at which the intentionally-emitted liφt would dazzle said viewer in combination with any other visible liφt that is intentionally emitted. 7. An arraiigemeπt according to Claim 6, ch ar a c ¬ ter i z ed in that the intentionally-emitted liφt is substan¬ tially yellow αr white liφt. 8. An arrangement according to Claim 6 o 7, charac¬ teri zed in that the headlanp (1) is constructed so that the ___itention._lly-e_id.tted visible liφt is emitted as an cuter frame (7) of light within which substantially only ultraviolet liφt is emitted. 9. An arrangement according to Claim 6, 7 αr8, charac¬ teriz ed in that the headlanp (1) is constructed so that the intentionally-emitted visible liφt is emitted in one (9) or several (10) points over the surface of the headlamp glass (4) , wherein substantially only ultraviolet liφt is emitted over the remaining surface (11; 12) of the headlamp glass (4) . 10. An arrangement according to any one of Claims 6-9, character i z ed in that the proportion of the surface of the headlamp glass (4) throuφ vfaich visible liφt is intentionally emitted is about 0.1 to 20%, preferably about 0.5 to 5%.

Inventors: BERGKVIST LARS A, FAST PEDER, BERGKVIST, LARS, A., FAST, PEDER
Applicants: ULTRALUX AB
Application year: 1992
Main classification: F21M3
IPC codes: B60Q1, F21S8, F21S10, F21V9