a2 United States Patent
`US 6,406,172 B1
`(10) Patent No.:
`Jun. 18, 2002
`(45) Date of Patent:
`Harbersetal.
`
`
`US006406172B1
`
`(54) HEADLAMP AND DYNAMIC LIGHTING
`SYSTEM FOR VEHICLES
`
`(75)
`
`Inventors: Gerard Harbers; Simon H. A.
`Begemann, both of Eindhoven (NL)
`(73) Assignee: Koninklijke Philips Electronics N.V.
`(NL)
`
`3/1999 Gotoh oo. 362/466
`8/1999 Gotoh ......
`4/2001 Begemann...
`5/2001 Borneret al... 362/235
`
`
`
`5,876,113 A *
`5,931,572 A *
`6,220,722 Bl *
`6,234,648 B1 *
`hed by examiner
`.
`:
`Primary Examiner—Sandra O’Shea
`Assisiant Examiner—Ronald E. DelGizzi
`(*) Notice: Subject to any disclaimer, the term of this|(74) Attorney, Agent, or Firm—Dicran Halajian
`patent is extended or adjusted under 35
`US.C. 154(b) by 0 days.
`GO)
`SESTae
`A headlamp(2; 3) of a vehicle (1) has a light source (4; 5)
`comprising a plurality of opto-electronic elements (11; 12;
`(21) Appl. No.: 09/599,792
`13; 14), preferably light-emitting diodes (LEDs). At least
`4.
`one of these opto-electronic elements (11; 12; 13; 14) has, in
`Filed:
`(22)
`Jun. 22, 2000
`
`
`
`
`
`‘ flux of51m or‘cati tort operation, a luminous higher. According to
`
`
`(30)
`Foreign Application Priority Data
`perati
`lumi
`flux
`of 5 1
`higher. According
`the invention, the spatial distribution of the light beam (6,
`Jun. 25, 1999
`(EP) wos cc eee eesee cess eneeenneeseees 99202054
`6',...; 7,7...) generated by the light source (4; 5) is
`(51)
`Int. Cl.”
`F21V 29/00
`continuously adjustable. Preferably, the light source (4; 5)
`(52) US. Che ccc362/544:36/545: 362/230:
`comprises opto-electronic elements (11; 12; 13; 14) only.
`ees "36231: 362/464
`Preferably, the spatial distribution is influenced by the speed
`.
`a of the vehicle (1), the rotational position of the steering
`(38) Hield of Seaneht sam:362/230.931. sera a6
`wheel of the vehicle (1), the weather conditions, and it can
`- ee also be influenced by the driver of the vehicle (1).
`(56)
`References Cited
`Preferably, the spectral characteristics of the light beam (6,
`6',...;7,7',...) generated by the light source (4; 5) depend
`U.S. PATENT DOCUMENTS
`on the position in the light beam (6, 6',...; 7, 7',...). The
`light beam comprisesat least two light beam segments (6,6';
`7, 7') having essentially different spectral characteristics.
`
`
`
`8/1992 Schoniger et al.
`5,136,483 A *
`.......... 362/545
`5,570,951 A * 11/1996 Bertling et al.
`...
`«. 362/231
`
`5,685,637 A
`11/1997 Chapmanetal. .
`... 362/263
`5,798,911 A *
`8/1998 Josic vee 362/466
`
`be
`
`24 Claims, 5 Drawing Sheets
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`US 6,406,172 Bl
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`1
`HEADLAMP AND DYNAMIC LIGHTING
`SYSTEM FOR VEHICLES
`
`CROSS REFERENCE TO RELATED
`APPLICATION
`
`Applicants’ application Ser. No. 09/599,792 filed Jun. 22,
`2000 discloses related subject matter.
`
`BACKGROUND OF THE INVENTION
`
`10
`
`The invention relates to a vehicle headlamp comprising a
`light source which includes a plurality of opto-electronic
`elements.
`
`2
`ferent material systems which can suitably be used for
`different regionsofthe 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 luminousflux enables a vehicle headlamp to
`be manutactured having much more dynamic lighting pos-
`sibilities 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 influ-
`cneed by conditions outside the vehicle, the so-called exter-
`nal 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 conditionsinside the vehicle, the so-called
`internal conditions. Internal conditions include, for example,
`the shapes of the light beam as set or 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 andoff in such a mannerthat the light beam can
`assume various shapes, which shapes may demonstrate a
`partial overlap and may, moreorless gradually, merge. The
`luminous flux of the opto-electronic elements may be
`changed with respect
`to each other. If a light beam is
`adjustable, also the intensity and/or spectral characteristic of
`the light beam, or of 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 or
`in the axis of the light beam, such as oncomingtraffic, 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, whichrefers to the visibility
`of objects which are situated in the center, or in the imme-
`diate 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 shoulderof 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 producesa light beam ofvisible
`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 embodimentof 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 vchicle headlamp is composed of onc type
`of light source. By combining LEDsor so-called multi-chip
`packages having a luminousflux in the range from 10-250
`lm, the luminous flux of a suitable combination of 25 such
`
`UNIFIED PATENTS EXHIBIT 1004
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`15)
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`-
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`,
`
`The invention also relates to a vehicle provided with a
`headlamp.
`Such headlampsare used on vehicles, suchas cars, trucks,
`buses, bicycles and on vessels and aircraft.
`Vehicle headlamps are knownper se. A vehicle headlamp
`generally comprises an electric lamp with an incandescent
`body, for example,
`in a halogen-containing inert gas (a
`so-called halogen lamp), or an electric lamp with a pair of
`electrodes in an ionizable gas (a so-called discharge lamp).
`Such headlamps are customarily built up of two light
`sources which,
`in operation, generate either a so-called ,
`passing beam or a so-called main beam. Vehicle headlamps
`arc known whereinthe light source for the passing beam and
`the light source for the main beam are housed in a single
`lamp vessel (the so-called H4). Other known vehicle head-
`lampsare those wherein two typesoflight sources are used,
`for example a halogen lamp in combination with a discharge
`lamp. There are also headlamps which, in operation, gener-
`ate colored light, which is generally brought about by a
`suitable coating provided on an outer surface of the lamp
`vessel. U.S. Pat. No. 5,685,637 discloses a vehicle headlamp ,
`wherein a halogen lamp is combined with a ring of light-
`emitting diodes (LEDs).
`The known vehicle headlamp has the drawback that, in
`principle, it constitutes a static lighting system.
`
`40
`
`SUMMARYOF THE INVENTION
`
`It is an object of the invention to provide a vehicle
`headlamp of the type described in the opening paragraph,
`which exhibits more dynamic lighting possibilities.
`To achieve this, the vehicle headlamp is characterized in
`accordance with the invention in that
`
`45
`
`a luminous flux of at least one of the opto-electronic
`elements amounts, in operation, to at least 5 lm,
`and in that a light beam generated by the light source has
`a continuously adjustable spatial distribution.
`Opto-electronic elements, also referred to as electro-
`optical elements, for example electroluminescent elements,
`suchaslight-emitting diodes (LEDs) with a luminous flux of
`5 Im or more can suitably be used as a light source for
`vehicle headlamps. A relatively high luminousflux is nec-
`essary 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 suffi-
`ciently clearly from a distance.
`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 mect
`internationally standardized and specified light beam inten-
`sities. Current technology of opto-electronic elements, par-
`ticularly that of light-emitting diodes, has yielded two dif-
`
`60
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`US 6,406,172 Bl
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`10
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`15)
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`4
`3
`the vehicle headlamp dazzles should not be too high, which
`elements, or fewer, preferably a combination of 15 such
`elements, or fewer, such as a combination of four such
`is achieved in that the driver adjusts the light beam so as to
`be relatively narrow.
`elements, meets the international standard ranging between
`An alternative embodiment of the vehicle headlamp is
`600 and 1000 Im. The dimensions of a vehicle headlamp
`characterized in accordance with the invention in that the
`comprising such a relatively small number of opto-
`spectral characteristic of a light beam generated by the light
`electronic elements are comparable to the dimensions of a
`source depends upon the position in the light beam. By
`conventional vehicle headlamp. An additional advantage of
`making the spectral characteristic of the light beam gener-
`the use of LEDs is that
`the service life of these opto-
`ated by the light source dependenton the position in the light
`electronic elements is very long as comparedto that of the
`beam, objects situated outside the center of the light beam
`conventional vehicle headlamp.
`can be better observed. Preferably, the light beam comprises
`In a preferred embodiment of the vehicle headlamp in
`at least two beam segments having a substantially different
`accordance with the invention, the spatial distribution of the
`spectral characteristic. In general, the intensity of the light
`light beam can be influenced by the velocity of the vehicle.
`beam emitted by a vehicle headlamp decreases as a function
`In this manner, the range and the width of the light beam can
`of the position in the light beam,i.e. the intensity is maximal
`be adjusted as a function of the velocity of the vehicle. At
`in the centerof the light beam and gradually decreases in the
`relatively low velocities, it is desirable for the light distri-
`direction of positions situated at a larger distance from the
`bution of the light beam to be wider, so that, for examp
`centerof the light beam. Asaresult, the intensity of the light
`also the shouldersofthe roadare illuminated. The higher the
`for so-called on-axis viewing is relatively much higher than
`velocity of the vehicle, the longer the braking distanceofthe
`for the so-called off-axis viewing.
`vehicle will be in general, so that it is desirable for the range :
`It is well-known that the sensitivity of the human eye
`of the light beam to increase. It may also be desirable for the
`changes with the wavelength of the light and that equal
`width of the light beam to decrease and/or the intensity
`quantities of energy of different wavelengths generally cause
`distribution between on-axis viewing and off-axis viewing to
`different sensations of brightness. In other words, if we
`change. By switching on or off one or more opto-electronic
`consider a spectrum, and the received energy (per unit of
`time) is equal for all wavelengths, the middle of the visible
`elements at specific limiting values of the velocity of the 2
`vehicle, a continuously adjustable spatial distribution of the
`region will apparently be brighter than the red and the blue
`light emitted by the vehicle headlamp is obtained.
`ends. If the intensity of the light is relatively high (luminous
`efficiency 23.5 cd/m*), the maximum of the brightness lies
`An embodiment of the vehicle headlamp is characterized
`at a wavelength of 555 nm (green/yellow), the so-called
`in accordance with the invention in that the spatial distri-
`bution of the light beam can be influenced bythe rotational
`photopic eye-sensitivity curve. At this wavelength, particu-
`position of a steering wheel of the vehicle. This enables the
`larly the cones are active in the human eye. If the intensity
`of the light is relatively low (luminous efficiency =0.035
`spatial distribution of the light beam of the vehicle headlamp
`cd/m’), the maximum of the brightness lies at a wavelength
`to be adapted to the position of the steering wheel of the
`of 507 nm (blue/green or cyanblue), the so-called scotopic
`vehicle. The light beam “rotates” simultaneously,as it were,
`with the desired direction of movementof the vehicle. When
`eye-sensitivity curve. 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 ight 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 unpleasantby the driver
`of the vehicle.
`Preferably, a first beam segment has a spectral character-
`istic whichis 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, ie. 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, Le.
`rich in blue-green light.
`
`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 ofthe rotational position
`of the steering wheel of the vehicle, a continuously adjust-
`able 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, whenthe 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 headlampis characterized
`in accordance with the invention in that the spatial distri-
`bution of the light beam can be influenced by a driverofthe
`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 examplea relatively narrow country road
`or a broad multi-lane motorway), the presence of bends and
`the possibility of oncomingtraffic, it becomes desirable to
`make the light distribution driver-adjustable. On a country
`road, it is desirable to have a relatively broad light distri-
`bution 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 oncomingtraffic, the degree to which
`
`40
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`US 6,406,172 Bl
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`These and other aspects of the invention will be apparent
`from and elucidated with reference to the embodiments
`described hereinafter.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`10
`
`15)
`
`FIG. 1A is a perspective view of a vehicle provided with
`a headlamp in accordance with the invention;
`FIG. 1B is a plan view of a part of the vehicle shown in
`FIG. 1A; and
`FIG. 2 is a sectional viewof a light source comprising a
`plurality of opto-electronic elements arranged in accordance
`with a regular pattern;
`FIG. 3A showsa 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 improving the on-axis observation
`conditions;
`FIG. 4A shows a relatively broad light beam which -
`predominantly consists of yellow light, and
`FIG. 4B showstherelatively 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 T‘igures are purely diagrammatic and not drawn to 2
`scale. Particularly for clarity, some dimensions are exagger-
`ated strongly. In the Figures, like reference numerals refer to
`like parts whenever possible.
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`FIG. 1A is a very diagrammatic, perspective view of a
`vehicle 1 situated on a road 10 and provided with a head-
`lamp 2; 3 in accordance with the invention. FIG. 1B is a
`diagrammatic, plan view of a part of the vehicle 1 shown in
`FIG. 1A.Each oneof the vehicle headlamps2; 3 is provided
`with a light source 4; 5, which emits (diverging) light beams
`6, 6',...3; 7, 7',... in a longitudinal direction 9. FIG. 1B
`further shows an imaginary screen 15 for trapping the light
`emitted by the light beams 6, 6'. In accordance with the
`invention,
`the spatial distribuiion of the light beams 6,
`6",...3; 7, 7... generated by the light source 4; 5 is
`continuously adjustable.
`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, whichfirst beam segment
`6; 7 comprises a kind of passing beam;
`a second beam segment6', 7' comprising a part of the light
`beam which is directed in particular towards the edge
`of the road (the shoulder of the road);
`third beam segment 6"; 7" comprising a relatively
`narrow part of the light beam, which is directed par-
`ticularly towards the center of the road, and the direc-
`tion of which 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"; 7comprises a kind of main beam,
`the spectral characteristic of the fourth beam segment
`6"; 7'" differing substantially from the spectral char-
`acteristic 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
`
`@
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`40
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`65
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`6
`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 ele-
`ments are arranged in the light source 5 may be mirror-
`inverted with respect to that in light source4. In addition, the
`number of opto-electronic elements 11; 12; 13; 14 in light
`source 4 does not have to be equalto that in light source 5.
`Thearray of opto-electronic elements 11; 12; 13; 14 does not
`have to be provided ona flat substrate, it may alternatively
`be provided on a curved substrate. The shape of the substrate
`on whichthe 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.
`In accordance with the invention, the luminousflux of at
`least one of the opto-electronic elements 11; 12; 13; 14 is at
`least 5 Im, in operation. Preferably, in operation, all opto-
`electronic elements 11; 12; 13; 14 have a luminous flux
`above 5 Im. Preferably, the vehicle headlamp 2; 3 is com-
`posed 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 luminousflux of 5 Im
`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
`oplo-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 ofa pluralityof light-emitting diodes
`(LEDs). In this example an array of 8x3 LEDs. For identi-
`fication purposes, in FIG. 2, the rows are indicated byletters
`A, B, C, and the columnsby digits 1-8. By using LEDsor
`so-called multi-chip packages with a luminous flux in the
`range from 10-250 Im 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 Im. The dimensions of a vehicle headlamp2; 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 byselectively switching on and off a numberof
`opto-electronic elements 11; 12; 13; 14,
`the light beams
`generated by the light source 4; 5 can berelatively readily
`subdivided into one or more beam segments 6, 6'; 7, 7'
`having a different spatial distribution or substantially differ-
`cnt spectral characteristics. The vehicle 1 or the hcadlamp 2;
`3 is preferably provided with means (not shown) for chang-
`ing the luminousflux of the opto-electronic elements 11; 12;
`13; 14 with respect to each other.
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`US 6,406,172 Bl
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`In the example shown in FIG. 2, red LEDs are indicated
`by reference numeral 11, green LEDs by reference numeral
`12, blue LEDsby reference numeral 13, and yellow or white
`LEDsbyreference. numeral 14. By ordering the LEDsin 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 effec-
`tively mix the colors originating from the LEDsareavail-
`able. This is important, in particular, to ensure that the red
`LEDsare not mistakenly taken for brake lights.
`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 whichare 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 itself.
`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 bythe
`imaginary screen 15 (see FIG. 1B),
`in which case an
`observer looks against the longitudinal direction 9. With
`reference to ['IG. 2, the first, so-called on-axis beam segment
`6,
`is generated by light beams originating from LEDs
`A1-A8 and B3-B5, while the second, so-called off-axis
`beam segment 6', is generated by light beams originating
`from LEDs B1, B2, C1 and C2. The other LEDs, as shown
`in FIG. 2, are switched off under these lighting conditions.
`FIG. 3B not only showsthe 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 charac-
`teristics 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 (bcam scgment 6) and/or of
`the off-axis beam segment 6'.
`In order to improve the visibility of the surroundings of 5
`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 adaptedto a light intensity which
`is relatively low. To obtain a good observation field at
`relatively low light intensities, preferably the spectral char-
`acteristic 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 third and fourth beam segments 6", 6'";
`7", 7" with a spectral characteristic whichis rich in white or
`yellow-orange light and by providing the second beam
`segment 6', 7' with a spectral characteristic which is rich in
`bluc-green light. By thus rendering the spectral character-
`istic of the light beam generated by the light source depen-
`dent upon the position in the light beam, objects situated
`outside the center of the light beam are better observed.
`
`40
`
`45
`
`60
`
`65
`
`8
`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 whichis substantially
`composed of yellow light. The absence of the blue compo-
`nent in the visible light causes the effect of backscattering to
`be substantially reduced.
`FIG. 4B showsthe 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 dynamicallyilluminated 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 manydifferent
`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 dimensionsof the light beamsare
`adjustable at will, for example, by creating a broader light
`beam (illuminating the shoulderof 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 face
`of the vehicle. A future increase in the efficiency and light
`output of the LEDs will enable the number of LEDsto 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 combinationof 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.
`Whatis claimedis:
`
`1. A headlamp of a vehicle comprising a light source
`which includes a plurality of opto-electronic elements,
`wherein:
`
`least one of the opto-electronic
`a luminous flux of at
`elements amounts, in operation, to at least 5 lm,
`the opto-electronic elements form an array distributed
`ev