(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
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`( 19) World Intellectual Property Organization
`International Bureau
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`I lllll llllllll II llllll lllll 11111111111111111111111111111111111111111111111111111
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`(43) International Publication Date
`4 January 2001 (04.01.2001)
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`PCT
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`(10) International Publication Number
`WO 01/01038 Al
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`: F21S 8/12, HOIL
`(51) International Patent Classification7
`25/075, B60Q 1/08, 1/12 // F21Y 101:02, F21W 101:10
`
`(74) Agent: MULDER, Cornelis, A., .M.; Intemationaal Oc(cid:173)
`trooibureau B.V., Prof Holstlaan 6, NL-5656 AA Eind(cid:173)
`hoven (NL).
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`(21) International Application Number:
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`PCT/EP00/05893
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`(22) International Filing Date:
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`23 June 2000 (23.06.2000)
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`(25) Filing Language:
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`(26) Publication Language:
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`English
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`English
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`(30) Priority Data:
`99202054.5
`
`25 June 1999 (25.06.1999) EP
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`(71) Applicant: KONINKLIJKE PHILIPS ELECTRON(cid:173)
`ICS N.V. [NL/NL]; Groenewoudseweg 1, NL-5621 BA
`Eindhoven (NL).
`
`(72) Inventors: HARBERS, Gerard; Prof. Holstlaan 6,
`NL-5656 AA Eindhoven (NL). BEGEMANN, Simon, H.,
`A.; Prof. Holstlaan 6, NL-5656 AA Eindhoven (NL).
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`(81) Designated States (national): CN, IN, JP, KR.
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`(84) Designated States (regional): European patent (AT, BE,
`CH, CY, DE, DK, ES, Fl, FR, GB, GR, IE, IT, LU, MC,
`NL, PT, SE).
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`Published:
`With international search report.
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`For two-letter codes and other abbreviations, refer to the "Guid(cid:173)
`ance Notes on Codes and Abbreviations" appearing at the begin(cid:173)
`ning of each regular issue of the PCT Gazette.
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`= (54) Title: VEHICLE HEADLAM:P AND A VEIIlCLE
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`t'°') (57) Abstract: A headlamp (2; 3) of a vehicle (1) has alight source (4; 5) comprising a plurality of opto-electronic elements (11; 12;
`~ 13; 14), preferably light-emitting diodes (LEDs). At least one of these opto-electronic elements (11; 12; 13; 14) has, in operation, a
`Q
`luminous flux of 5 lm or higher. According to the invention, the spatial distribution of the light beam (6, 6', ... ; 7, T, ... ) generated
`..._ by the light source (4; 5) is continuously adjustable. Preferably, the light source (4; 5) comprises opto-electronic elements (11; 12;
`;
`13; 14) only. Preferably, the spatial distribution is influenced by the speed of the vehicle (1), the rotational position of the steering
`wheel of the vehicle ( 1 ), the weather conditions, and it can also be influenced by the driver of the vehicle (I). Preferably, the spectral
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`0 characteristics of the light beam (6, 6', ... ; 7, 7', ... ) generated by the light source (4; 5) depend on the position in the light beam
`> (6, 6', ... ; 7, 7', .... ). The light beam comprises at least two light beam segments (6, 6'; 7, 7') having essentially different spectral
`~ characteristics.
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`PCNA Ex. 1011
`U.S. Patent 11,208,029
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`WO 01/01038
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`PCT /EP00/05893
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`Vehicle headlamp and a vehicle.
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`The invention relates to a vehicle headlamp comprising a light source which
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`includes a plurality of opto-electronic elements.
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`The invention also relates to a vehicle provided \vith a headlamp.
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`Such headlamps are used on vehicles, such as cars, trucks, buses, bicycles and
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`on vessels and aircraft.
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`Vehicle headlamps are known per se. A vehicle headlamp generally comprises
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`an electric lamp with an incandescent body, for example, in a halogen-containing inert gas (a
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`so-called halogen lamp), or an electric lamp with a pair of electrodes in an ionizable gas (a so(cid:173)
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`called discharge lamp). Such headlamps are customarily built up of two light sources which, in
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`operation, generate either a so-called passing beam or a so-called main beam. Vehicle
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`headlamps are known wherein the light source for the passing beam and the light source for
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`the main beam are housed in a single lamp vessel (the so-called H4). Other known vehicle
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`headlamps are those wherein two types of light sources are used, for example a halogen lamp
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`in combination with a discharge lamp. There are also headlamps which, in operation, generate
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`colored light, which is generally brought about by a suitable coating provided on an outer
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`surface of the lamp vessel. US-A 5 685 637 discloses a vehicle headlamp wherein a halogen
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`lamp is combined with a ring of light-emitting diodes (LEDs).
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`The known vehicle headlamp has the drawback that, in principle, it constitutes a
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`static lighting system.
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`It is an object of the invention to provide a vehicle headlamp of the type
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`described in the opening paragraph, which exhibits more dynamic lighting possibilities.
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`To achieve this, the vehicle headlamp is characterized in accordance with the
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`invention in that
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`a luminous flux of at least one of the opto-electronic elements amounts, in
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`operation, to at least 5 lm,
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`and in that a light beam generated by the light source has a continuously
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`adjustable spatial distribution.
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`Opto-electronic elements, also referred to as electro-optical elements, for
`example electroluminescent elements, such as light-emitting diodes (LEDs) with a luminous
`flux of 5 lm or more can suitably be used as a light source for vehicle headlamps. A relatively
`high luminous flux is necessary to ensure that also under ambient light conditions, for example
`sunlight or light originating from headlamps of other vehicles, sufficient light is generated so
`that a light beam generated by the light source can be observed sufficiently clearly from a
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`distance.
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`To generate a so-called passing beam and/or a so-called main beam, a
`conventional vehicle headlamp requires a luminous flux ranging between 600 and 1000 Im to
`10 meet internationally standardized and specified light beam intensities. Current technology of
`opto-electronic elements, particularly that of light-emitting diodes, has yielded two different
`material systems which can suitably be used for different regions of the visible spectrum, i.e.
`Al-In-Ga-N for blue-green light and Al-In-Ga-P for yellow-red light. As a result, any desired
`spectral characteristic can be produced by combining suitable light-emitting diodes.
`The use of a plurality of opto-electronic elements with a relatively high
`luminous flux enables a vehicle headlamp to be manufactured having much more dynamic
`lighting possibilities than the known vehicle headlamp. The opto-electronic elements can be
`switched on and switched off, with the spatial distribution of the generated light beam
`depending on the conditions. Said conditions may be influenced by conditions outside the
`vehicle, the so-called external conditions. External conditions include, for example, the
`general lighting level (day or night situation), the shape of the road (width, number of bends),
`the weather conditions (bright weather, fog, rain, snow, etc.) and the velocity at which and/or
`the direction in which the vehicle is moving. Conditions which also influence the spatial
`distribution may be determined by conditions inside the vehicle, the so-called internal
`conditions. Internal conditions include, for example, the shapes of the light beam as set or
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`desired by the driver.
`In the description of the current invention, a light beam having a continuously
`adjustable spatial distribution is to be taken to mean that the opto-electronic elements can be
`switched on and off in such a manner that the light beam can assume various shapes, which
`shapes may demonstrate a partial overlap and may, more or less gradually, merge. If a light
`beam is adjustable, also the intensity and/or spectral characteristic of the light beam, or of
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`segments of the light beam. may be different.
`Since the spatial distribution is (continuously) adjustable, the driver's view of
`the road and the surroundings of the vehicle is improved. On the one hand, objects situated on
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`or in the axis of the light beam, such as oncoming traffic, can be better observed. On the other
`hand, also the observation of objects outside the center of the light beam is improved. This
`observation of objects outside the center of the light beam is also referred to as off-axis
`viewing, as opposed to the so-called on-axis viewing, which refers to the visibility of objects
`5 which are situated in the center, or in the immediate vicinity of the center, of the light beam.
`Examples of off-axis viewing include the observation of objects situated at or near the edge of
`the field of vision of the driver of the vehicle, for example the shoulder of the road, (unlit)
`objects, such as pedestrians or cyclists at the edge of the road on which the vehicle is traveling,
`and the observation of vehicles traveling on a road which crosses the road on which the
`vehicle provided with the headlamp in accordance with the invention is traveling.
`The known vehicle headlamp has two light sources, namely a halogen lamp and
`a ring of light-emitting diodes, however, the halogen lamp produces a light beam of visible
`light and the LEDs emit infrared light at 880 nm. The individual light beams of the known
`vehicle headlamp are static in character and the light beam generated by the light source does
`not have a continuously adjustable spatial distribution.
`An embodiment of the vehicle headlamp is characterized in accordance with the
`invention in that the light source consists of a plurality of opto-electronic elements.
`Consequently, the vehicle headlamp is composed of one type oflight source. By combining
`LEDs or so-called multi-chip packages having a luminous flux in the range from 10-250 lm,
`the luminous flux of a suitable combination of 25 such elements, or fewer, preferably a
`combination of 15 such elements, or fewer, such as a combination of four such elements,
`meets the international standard ranging between 600 and 1000 lm. The dimensions of a
`vehicle headlamp comprising such a relatively small number of opto-electronic elements are
`comparable to the dimensions of a conventional vehicle headlamp. An additional advantage of
`the use of LEDs is that the service life of these opto-electronic elements is very long as
`compared to that of the conventional vehicle headlamp.
`In a preferred embodiment of the vehicle headlamp in accordance with the
`invention, the spatial distribution of the light beam can be influenced by the velocity of the
`vehicle. In this manner, the range and the width of the light beam can be adjusted as a function
`of the velocity of the vehicle. At relatively low velocities, it is desirable for the light
`distribution of the light beam to be wider, so that, for example, also the shoulders of the road
`are illuminated. The higher the velocity of the vehicle, the longer the braking distance of the
`vehicle will be in general, so that it is desirable for the range of the light beam to increase. It
`may also be desirable for the width of the light beam to decrease and/or the intensity
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`distribution between on-axis viewing and off-axis viewing to change. By switching on or off
`one or more opto-electronic elements at specific limiting values of the velocity of the vehicle,
`a continuously adjustable spatial distribution of the light emitted by the vehicle headlamp is
`obtained.
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`An embodiment of the vehicle headlamp is characterized in accordance with the
`invention in that the spatial distribution of the light beam can be influenced by the rotational
`position of a steering wheel of the vehicle. This enables the spatial distribution of the light
`beam of the vehicle headlamp to be adapted to the position of the steering wheel of the
`vehicle. The light beam "rotates" simultaneously, as it were, with the desired direction of
`10 movement of the vehicle. When the steering wheel is rotated it may be desirable for the
`intensity of the light beam shining in a straight line to decrease. By switching on or off one or
`more opto-electronic elements at specific limiting values of the rotational position of the
`steering wheel of the vehicle, a continuously adjustable spatial distribution of the light emitted
`by the vehicle headlamp is obtained.
`In a favorable embodiment of the vehicle headlamp in accordance with the
`invention, the spatial distribution of the light beam can be influenced by the weather
`conditions. Under unfavorable weather conditions, in particular fog and snow, when the
`visibility is reduced by backscattering from fog or snow particles, the shape of the light beam
`can be adapted by activating different combinations of opto-electronic elements and by
`changing the output levels of the different opto-electronic elements. As a result of these
`adaptations, the overall spatial distribution of the light is changed.
`An embodiment of the vehicle headlamp is characterized in accordance with the
`invention in that the spatial distribution of the light beam can be influenced by a driver of the
`vehicle. This enables the spatial distribution, for example the range and/or the width of the
`light beam, to be adjusted by the driver. As a result of information regarding, for example, the
`road type (for example a relatively narrow country road or a broad multi-lane motorway), the
`presence of bends and the possibility of oncoming traffic, it becomes desirable to make the
`light distribution driver-adjustable. On a country road, it is desirable to have a relatively broad
`light distribution of the light beam, so that also the shoulders of the road are clearly
`illuminated. On a motorway, where it is likely that there will be oncoming traffic, the degree
`to which the vehicle headlamp dazzles should not be too high, which is achieved in that the
`driver adjusts the light beam so as to be relatively narrow.
`An alternative embodiment of the vehicle headlamp is characterized in
`accordance with the invention in that the spectral characteristic of a light beam generated by
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`the light source depends upon the position in the light beam. By making the spectral
`characteristic of the light beam generated by the light source dependent on the position in the
`light beam, objects situated outside the center of the light beam can be better observed.
`Preferably, the light beam comprises at least two beam segments having a substantially
`different spectral characteristic. In general, the intensity of the light beam emitted by a vehicle
`headlamp decreases as a function of the position in the light beam, i.e. the intensity is maximal
`in the center of the light beam and gradually decreases in the direction of positions situated at
`a larger distance from the center of the light beam. As a result, the intensity of the light for so(cid:173)
`called on-axis viewing is relatively much higher than for the so-called off-axis viewing.
`It is well-known that the sensitivity of the human eye changes with the
`wavelength of the light and that equal quantities of energy of different wavelengths generally
`cause different sensations of brightness. In other words, if we consider a spectrum, and the
`received energy (per unit of time) is equal for all wavelengths, the middle of the visible region
`will apparently be brighter than the red and the blue ends. If the intensity of the light is
`relatively high (luminous efficiency;::: 3.5 cd/m2
`), the maximum of the brightness lies at a
`wavelength of 555 nm (green/yellow), the so-called photopic eye-sensitivity curve. At this
`wavelength, particularly the cones are active in the human eye. If the intensity of the light is
`relatively low (luminous efficiency:::; 0.035 cd/m2
`), the maximum of the brightness lies at a
`wavelength of 507 nm (blue/green or cyanblue), the so-called scotopic eye-sensitivity curve.
`20 At this wavelength, particularly the rods are active in the human eye.
`It is advantageous to bring about substantially different spectral characteristics
`of the light beam for the on-axis and the off-axis parts of the light beam. In particular, in the
`off-axis parts of the light beam, the spectral characteristic of the light is adapted to a light
`intensity which is relatively low. By thus making the spectral characteristic of the light beam
`generated by the light source dependent upon the position in the light beam, the visibility of
`objects situated outside the center of the light beam is improved.
`It is noted that, in practice, also photopic and scotopic light beams preferably
`have a broad spectrum, which light beams both have a more or less "white" appearance. The
`difference between a photopic and a scotopic light beam corresponds, as it were, to a
`difference between a light beam having a high and a low color temperature.
`There is a possibility that the above-mentioned beam segments may comprise
`segments demonstrating a partial overlap. A possibly non-continuous transition between the
`beam segments may be perceived as unpleasant by the driver of the vehicle.
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`PCT /EP00/05893
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`6
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`Preferably, a first beam segment has a spectral characteristic which is rich in
`green-yellow light, and a second beam segment has a spectral characteristic which is rich in
`blue-green light. On the one hand, in the on-axis part of the light beam (the first beam
`segment) a spectral characteristic of the light is presented which is adapted to the photopic
`eye-sensitivity curve, i.e. rich in green-yellow light. On the other hand, in the off-axis parts of
`the light beam (the second beam segment) a spectral characteristic of the light is presented
`which is adapted to the scotopic eye-sensitivity curve, i.e. rich in blue-green light.
`These and other aspects of the invention will be apparent from and elucidated
`with reference to the embodiments described hereinafter.
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`In the drawings:
`Fig. IA is a perspective view of a vehicle provided with a headlamp in
`
`accordance with the invention;
`Fig. lB is a plan view of a part of the vehicle shown in Fig. IA; and
`Fig. 2 is a sectional view of a light source comprising a plurality of opto-
`electronic elements arranged in accordance with a regular pattern;
`Fig. 3A shows a light beam generated by a first beam segment in combination
`with a so-called off-axis light beam generated by a second beam segment;
`Fig. 3B shows the light beams of Fig. 3A and two additional light beams for
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`improving the on-axis observation conditions;
`Fig. 4A shows a relatively broad light beam which predominantly consists of
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`yellow light, and
`Fig. 4B shows the relatively broad light beam of Fig. 4A in combination with a
`side light beam dependent upon the position of the steering wheel of the vehicle.
`These Figures are purely diagrammatic and not drawn to scale. Particularly for
`clarity, some dimensions are exaggerated strongly. In the Figures, like reference numerals
`refer to like parts whenever possible.
`Fig. 1 A is a very diagrammatic, perspective view of a vehicle 1 situated on a
`road 10 and provided with a headlamp 2; 3 in accordance with the invention. Fig. lB is a
`diagrammatic, plan view of a part of the vehicle 1 shown in Fig. lA. Each one of the vehicle
`headlamps 2; 3 is provided with a light source 4; 5, which emits (diverging) light beams 6, 6',
`... ; 7, 7', ... in a longitudinal direction 9. Fig. lB further shows an imaginary screen 15 for
`trapping the light emitted by the light beams 6, 6'. In accordance with the invention, the spatial
`distribution of the light beams 6, 6', ... ; 7, 7', ... generated by the light source 4; 5 is
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`continuously adjustable.
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`PCT /EP00/05893
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`In the example shown in Fig. lB, each one of the light beams originating from
`the light source 4; 5 of the vehicle headlamp 2; 3 is subdivided into four beam segments 6, 6',
`6", 6"'; 7, 7', 7", 7'", namely in:
`a first beam segment 6; 7 comprising a relatively wide, central part of the light
`beam, which first beam segment 6; 7 comprises a kind of passing beam;
`a second beam segment 6', 7' comprising a part of the light beam which is
`directed in particular towards the edge of the road (the shoulder of the road);
`a third beam segment 6"; 7" comprising a relatively narrow part of the light
`beam, which is directed particularly towards the center of the road, and the direction of which
`10 may be dependent upon the rotational position of the steering wheel of the vehicle;
`and a fourth beam segment 6"'; 7"' comprising a relatively narrow central part
`of the light beam, which fourth beam segment 6'"; 7"' comprises a kind of main beam, the
`spectral characteristic of the fourth beam segment 6"'; 7"' differing substantially from the
`spectral characteristic of the other beam segments 6, 6', 6"; 7, 7', 7".
`The light beams may also be composed of more than four beam segments, for
`example five or more beam segments having different spatial distributions and/or different
`spectral characteristics. In general, the light originating from two or more beam segments
`demonstrates an overlap. Partly because of the generally diverging character of the light
`beams, overlap between the various beam segments 6, 6', 6", 6"'; 7, 7', 7", 7'" is unavoidable.
`Fig. 2 is a sectional view of the light source 4 comprising a plurality of opto-
`electronic elements 11; 12; 13; 14 which are arranged in accordance with a regular pattern.
`Similarly, a plurality of opto-electronic elements may be provided in the light source 5 (not
`shown). The pattern in which the opto-electronic elements are arranged in light source 4 may
`differ from that in light source 5. For example, for reasons of symmetry, the pattern in which
`the opto-electronic elements are arranged in the light source 5 may be mirror-inverted with
`respect to that in light source 4. In addition, the number of opto-electronic elements 11; 12; 13;
`14 in light source 4 does not have to be equal to that in light source 5. The array of opto(cid:173)
`electronic elements 11; 12; 13; 14 does not have to be provided on a flat substrate. it may
`alternatively be provided on a curved substrate. The shape of the substrate on which the array
`of opto-electronic elements 11; 12; 13; 14 is provided is determined to a substantial degree by
`the desired direction of the light beams emitted by the various opto-electronic elements 11; 12;
`13; 14.
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`In accordance with the invention, the luminous flux of at least one of the opto(cid:173)
`electronic elements 11; 12; 13; 14 is at least 5 lm, in operation. Preferably, in operation, all
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`opto-electronic elements 11; 12; 13; 14 have a luminous flux above 5 lm. Preferably, the
`vehicle headlamp 2; 3 is composed of a single type of light source 4; 5. In other words. the
`light source 4; 5 is preferably exclusively composed of a plurality of opto-electronic elements
`11; 12; 13; 14.
`If opto-electronic elements with a luminous flux of 5 lm or more are to be
`efficiently employed, it is desirable to provide the vehicle headlamp with heat-dissipating
`means. For example, the substrate on which the opto-electronic elements 11; 12; 13; 14 are
`provided may consist of a metal or a metal alloy. As a result, a good heat conduction from the
`opto-electronic elements 11; 12; 13; 14 to the substrate is achieved.
`In the example shown in Fig. 2, the light source 4; 5 is exclusively composed of
`a plurality of light-emitting diodes (LEDs). In this example an array of 8 x 3 LEDs. For
`identification purposes, in Fig. 2, the rows are indicated by letters A, B, C, and the columns by
`digits 1-8. By using LEDs or so-called multi-chip packages with a luminous flux in the range
`from 10-250 lm for blue, yellow/orange, red and green light, the luminous flux of a suitable
`combination of 25 such elements, or fewer, preferably a combination of 15 such elements, or
`fewer, for example a combination of 4 such elements meets the internationally standardized
`and specified intensities for generating the passing beam and/or the main beam, which
`intensities range between 600 and 1000 lm. The dimensions of a vehicle headlamp 2; 3 having
`such a relatively small number of opto-electronic elements 11; 12; 13; 14 are comparable to,
`or much smaller than, the dimensions of a conventional vehicle headlamp.
`By using a plurality of opto-electronic elements 11; 12; 13; 14, and by
`selectively switching on and off a number of opto-electronic elements 11; 12; 13; 14, the light
`beams generated by the light source 4; 5 can be relatively readily subdivided into one or more
`beam segments 6, 6'; 7, 7' having a different spatial distribution or substantially different
`spectral characteristics. The vehicle 1 or the headlamp 2; 3 is preferably provided with means
`(not shown) for changing the luminous flux of the opto-electronic elements 11; 12; 13; 14 with
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`respect to each other.
`In the example shown in Fig. 2, red LEDs are indicated by reference numeral
`11, green LEDs by reference numeral 12, blue LEDs by reference numeral 13, and yellow or
`30 white LEDs by reference numeral 14. By ordering the LEDs in the manner indicated in Fig. 2,
`a substantial reduction of possible color effects is achieved for an observer looking into the
`light emitted by the vehicle headlamp (for example an oncoming car). In addition, optical
`systems which effectively mix the colors originating from the LEDs are available. This is
`important, in particular, to ensure that the red LEDs are not mistakenly taken for brake lights.
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`The example of the array of LEDs as shown in Fig. 2 represents an integrated
`module generating at least four types of light beams, namely various light beams which are
`switched on or off in dependence upon the velocity of the vehicle ( sidelamps, passing beam,
`main beam), light beams which are switched on in dependence upon the rotational position of
`the steering wheel, light beams for bad weather conditions, and light beams which are
`specially adapted for use in areas where the intensity of the light is relatively low.
`The ordering, providing and selectively switching on and off of opto-electronic
`elements 11; 12; 13; 14 in the form of an array may also be considered as an invention in
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`itself.
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`Fig. 3A shows a light beam generated by a first beam segment 6 in combination
`with a so-called off-axis light beam generated by a second beam segment 6'. The light
`originating from the beam segments 6, 6' is trapped by the imaginary screen 15 (see Fig. lB),
`in which case an observer looks against the longitudinal direction 9. With reference to Fig. 2,
`the first, so-called on-axis beam segment 6, is generated by light beams originating from LEDs
`15 A l-A8 and B3-B5, while the second, so-called off-axis beam segment 6', is generated by light
`beams originating from LEDs B 1, B2, C 1 and C2. The other LEDs, as shown in Fig. 2, are
`switched off under these lighting conditions.
`Fig. 3B not only shows the light beams shown in Fig. 3 but also two additional
`light beams which predominantly serve to improve the on-axis observation conditions. By
`additionally switching on the yellow or white LEDs C3-C5, a third beam segment 6" is
`obtained. and by additionally switching on the yellow or white LEDs B6, C6 and C7, a fourth
`beam segment 6"' is obtained. The spectral characteristics of the first beam segment 6 and the
`third and fourth beam segment 6", 6''' may be different. For example, it may be desirable to
`increase, in the beam segment 6 ", the quantity of in particular yellow light in order to improve
`the long-distance visibility. It may also be desirable, upon switching on the main beam (beam
`segment 6"), to switch off a part of the passing beam (beam segment 6) and/or of the off-axis
`beam segment 6'.
`In order to improve the visibility of the surroundings of the vehicle 1, a
`substantially different spectral characteristic of the light beam is brought about between the
`on-axis parts and the off-axis parts of the light beam. In particular. in the off-axis beam
`segment 6', 7' of the light beam, the spectral characteristic of the light is adapted to a light
`intensity which is relatively low. To obtain a good observation field at relatively low light
`intensities, preferably the spectral characteristic of one of the beam segments 6'; 7' is
`mesotopically tuned. This can be achieved by providing the first beam segment 6; 7 and the
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`third and fourth beam segments 6", 6'"; 7", 7"' with a spectral characteristic which is rich in
`white or yellow-orange light and by providing the second beam segment 6', 7' with a spectral
`characteristic which is rich in blue-green light. By thus rendering the spectral characteristic of
`the light beam generated by the light source dependent upon the position in the light beam,
`objects situated outside the center of the light beam are better observed.
`Under unfavorable weather conditions, in particular fog and snow, when
`visibility is reduced by backscattering caused by fog or snow particles, both the configuration
`and the spectral composition of the light beams generated by the light source 4; 5 can be
`adapted by activating different combinations of LEDs and by changing the output levels of the
`various LEDs. As a result of these adaptations, the spatial and/or spectral distribution of the
`light is changed. An example of such an adaptation is shown in Fig. 4A, wherein a relatively
`wide beam 16 is obtained which is substantially composed of yellow light. The absence of the
`blue component in the visible light causes the effect of backscattering to be substantially
`reduced.
`
`Fig. 4B shows the relatively wide beam 16 of Fig. 4A in combination with a
`side light beam 16' whose shape and intensity and position are dependent upon the position of
`the steering wheel of the vehicle 1. Such a side light beam 16' is preferably not switched on
`until the steering wheel of the vehicle exceeds a predetermined limiting angle when taking a
`bend or turning off. In this manner, the surface area and space wherein the vehicle is situated
`and where the vehicle is heading are dynamically illuminated as early as possible.
`In general, the LED modules operate at a low-voltage direct current, so that
`they can be advantageously employed in a vehicle.
`It will be obvious that within the scope of the invention many variations are
`possible to those skilled in the art. For example, the vehicle headlamp may have many
`different shapes, such as (rect)angular, round, oval, etc. One or more opto-electronic elements
`may also be suitable for use as indicator. In principle, the dimensions of the light beams are
`adjustable at will, for example, by creating a broader light beam (illuminating the shoulder of
`the road) at a lower speed of the vehicle, or by narrowing the beam at a relatively high speed.
`In addition, as a result of the large freedom of choice resulting from the use of (exclusively)
`opto-electronic elements, the location of the vehicle headlamp is no longer limited to the
`conventional location (at the front of the vehicle just above the road surface). It may be
`desirable to provide at least a part of the opto-electronic elements near the windscreen of the
`vehicle 1. It is also possible to provide a further part of the opto-electronic elements on a side
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`face of the vehicle. A future increase in the efficiency and light output of the LEDs will enable
`the number of LEDs to be further reduced.
`The scope of protection of the invention is not limited to the above examples.
`The invention is embodied in each novel characteristic and each combination of
`characteristics. Reference numerals in the claims do not limit the scope of protection thereof.
`The use of the term "comprising" does not exclude the presence of elements other than those
`mentioned in the claims. The use of the word "a" or "an" before an element does not exclude
`the presence of a plurality of such elements.
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`CLAIMS:
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`A headlamp (2; 3) of a vehicle ( 1) comprising a light source ( 4; 5) which
`1.
`includes a plurality of opto-electronic elements (11; 12; 13; 14), characterized in that
`a luminous flux of at least one of the opto-electronic elements ( 11; 12; 13; 14)
`amounts, in operation, to at least