DARMSTADT
`UNIVERSITY OF
`TECHNOLOGY
`
`PROGRESS IN AUTOMOBILE LIGHTING
`
`Department of Lighting Technology
`September 28/29, 1999
`
`FOUNTAIN AT MATHILDENHOHE, DARMSTADT
`
`VWGoA EX1023
`U.S. Patent No. 11,208,029
`
`
`UNIVERSITY OF
`TECHNOLOGY
`
`PROGRESS IN AUTOMOBILE LIGHTING
`
`Department of Lighting Technology
`September 28/29, 1999
`
`FOUNTAIN AT MATHILDENHOHE, DARMSTADT
`
`VWGoA EX1023
`U.S. Patent No. 11,208,029
`
`
`
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`dedicated to
`
`Mr. Reinhard Ropke
`
`
`
`28 I 29 September, 1999
`
`Proceedings of the Conference
`
`Lichttechnik Darmstadt
`
`Published by
`
`Prof. Dr.-lng. H.-J. Schmidt-Clausen
`Darmstadt University of Technology
`
`Eigentum der
`AUDIAG
`D-85045 lngolst.R..-,1,
`
`UTZ
`Herbert Utz Verlag - Wissenschaft
`Mi..inchen 1999
`
`
`
`ISBN 3-89675-920-5
`
`PAL '99: 2 Volumes, Vol. 5 & Vol. 6; not to be sold separately
`
`Die Deutsche Bibliothek- CIP-Einheitsaufnahme
`Progress in automobile lighting/ Darmstadt, University of Technology,
`Department of Lighting Technology. Publ. by. H.-J. Schmidt-Clausen. -
`Munchen : Utz, Wiss.
`Vol. 6. PAL '99 : 28./29. September, 1999 ; proceedings of the conference/
`Lichttechnik Darmstadt. - 1999
`ISBN 3-89675-920-5
`
`Das Werk ist urheberrechtlk:h geschutzt. Die dadurch begrundeten Rechte, insbesondere die der Ober(cid:173)
`setzung, des Nachdrucks, der Entnahme von Abbildungen, der Funksendung, der Wiedergabe auf photo(cid:173)
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`benutzt werden durften.
`
`Copyright © 1999 Herbert Utz Verlag GmbH
`
`Druck: drucken + binden gmbh, Munchen
`
`Herbert Utz Verlag GmbH, Munchen
`Tel.: 089-277791-00
`Fax: 089-277791-0.1
`utz@utzverlag.com
`www.utzverlag.com
`
`
`
`ADAPTIVE LIGHTING SYSTEMS:
`TECHNICAL SOLUTIONS AND A METHODOLOGICAL
`APPROACH FOR PHOTOMETRIC SPECIFICATIONS
`
`G~ Manassero and A. Paolini 1Y1agneti Marem Lighting Div.
`S. Battaglino, C.Bigliati and S .. Sinesi,' Fiat Research Center
`
`Introduction
`
`Safety and comfort, during driving conditions, are becoming more and more
`
`demanded from the market even for medium-low class vehicles. The headlamp,
`
`and hence the visibility improvement during low light conditions, is one of the
`
`components or devices of a vehicle on which there is a strong activity in
`
`Europe, also in the frame of the EUREKA 1403 project, and in Japan in order to
`
`have a more effective and flexible light utilisation. Market surveys have
`
`revealed that drivers demand headlights with different and better performances
`
`in comparison with existing systems. Although a modern lighting system for
`
`motor vehicles would preferably fit numerous ambient conditions such as
`
`twilight, dawn, adverse weather (mist, rain, fog), and tunnels, it has to be noted
`
`that the highest demands are given to better illumination under bad weather
`
`conditions, in curves and at high speed on highway and motor-way.
`
`In spite of the continuous improvement of both projection and reflection
`
`systems with either halogen or xenon gas discharge lamps, limitations still
`
`persist because the present systems are static, while night driving calls for a
`
`dynamic behaviour. The solution to the problem requires the definition of the
`
`most appropriate light distribution patterns and the switching strategy among
`
`the available light distributions.
`
`Adaptive Lighting Systems
`
`The function "Adaptive front-lighting" i$. provided through system that tunes the
`
`beam pattern in relations to driving, weather and environment conditions. The
`
`main sub-functions are:
`
`• Bending:
`
`514
`
`
`
`the purpose is to illuminate the curved lane to follow easier the trajectory;
`• High speed or motorway lighting:
`the visibility distance as a functionof the speed
`the purpose is to increase
`
`keeping glare at low level;
`
`• Country lighting:
`this beam pattern is mainly a low beam with a wider aperture angle which
`provides a good visilbility of the road edges;
`
`• Town driving
`a wide pattern is proposed to illuminate crossings, pedestrians and traffic
`
`signs;
`• Adverse weather lighting (wet road, mist and fog):
`in presence of fog or mist the beam is shaped to reduce backscattering,
`on the wet road the beam is modifyed to reduce the glare caused by the direct
`reflection from the wet road;_
`• Dawn, sunset, tunnel:
`automatic switching on is provided passing from daylight to
`illumination.
`
`low ambient
`
`Technical approaches
`There are several techniques and strategies to implement hardware solutions,
`but essentially they can grouped in two main categories:
`
`• beams from several lamps added to a basic beam (ref. 1)
`• movements of mechanical-optical parts to provide all the additional lighting
`functions (ref. 2).
`
`The development strategy has been to generate novel front-lighting systems
`starting from the existing regulations and from the -- requests on bending and
`high speed functions.
`
`Towards the implementation of all the above functions a lighting system with
`halogen lamps (Fig. 1) has been developed. It consists of sensors (speed,
`curve, external illumination intensity, presence of incoming vehicles, weather
`
`515
`
`
`
`conditions) linked to a dedicated microprocessor. This ECU drives the optical
`components via actuators and then offers all the functions described above
`
`(Fig.2a).
`
`The system architecture is shown in figure 2b.
`
`Fig. 1 - Adaptive headlight demonstrator
`
`adaptative headlamp
`beam
`bending
`
`country light
`
`Fig. 2a Adaptive Lighting System logic
`
`516
`
`
`
`rai11 sensor
`
`speed sensor
`
`adaptative sensor
`
`crossing vehicle ~e11sor
`
`adaptative optic
`
`-'Yslen,
`
`control unit
`
`Fig. 2b - System architecture
`
`Two arrays of lenses provide a continually adaptable beam that complements
`
`the main low beam. Relative movements of the two lens arrays shape the light
`
`distributions according to the SW strategy and the input conditions Specifically
`
`the transverse displacements of the arrays deflect the beam direction in
`
`relation to the steering angle, while the longitudinal displacements of them
`
`manage the beam divergence. Increasing the vehicle speed (Motorway beam)
`
`the additional light pattern gets narrower and improve the visibility distance. On
`
`the other·hand a wide spread additional beam is obtained in an urban scenario.
`
`Road tests methodology for photometric specifications
`
`The eye contrast sensitivity measurement versus light beams characteristics
`
`has been carried out using a scientific methodology. The optical specifications
`
`for the new light beams have been set.
`
`Figures 3a and 3b show driver's visual field mapping relative to the obstacles in
`
`visual scenario: lateral positions of signs, pedestrians, lane markings and
`
`generic obstacles on the lane for different distances (25, 40, 80, 120, 200
`
`517
`
`
`
`meters) are projected on the vertical screen ·at 25 meters from the driver. In
`these points were located, during field-tests· in order to measure the contrast
`sensitivity of the driver-subject (figure 3c), calibrated visual stimuli with different
`values of sinusoidal luminous contrasts and pattern frequencies (Fig.3d). This
`methodology has based on the fact that for not so wide visual stimuli and near
`.
`the visibility threshold, the human eye is a linear filter and any kind of visual
`stimulus can be broken up in a sum of visual stimuli with sinusoidal luminous
`contrast.
`
`~
`
`.
`
`.
`
`VISUAL FIELD MAPPING FOR COUNTRY DRIVING
`
`"'
`
`~L_t'lS at
`9BST"
`lat< al signs
`IA -
`I -L-i edestria.1 s
`
`:-1.~3.Q.J Q..m:
`
`~ ~
`
`M -ob tacles or Jane
`
`<I'
`
`l
`
`'
`B!l~-~~
`i
`l Q ARE~
`'
`l D ~,"
`~ar mirr rs al .o~ ~~."IU;
`m
`i
`D = oncou in2: driv r's eves at 25, 40 80mf
`
`I\
`
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`
`..
`
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`
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`
`2
`
`0
`
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`
`-2
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`
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`
`B
`
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`
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`
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`
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`
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`
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`r
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`---..._____
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`
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`------:
`
`..
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`~ ::,
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`
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`
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`
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`
`/
`
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`
`-14
`
`-12
`
`-10
`
`-8
`
`-G
`
`-4
`
`-2
`
`8
`
`10
`
`12
`
`Fig. 3a - Driver's visual field mapping during road tests in country
`
`driving conditions
`
`518
`
`
`
`VISUAL FIELD MAPPING FOR MOTORWAY DRIVING
`
`'<!<
`
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`
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`
`4
`
`3
`
`2
`
`-1
`
`-2
`
`-3
`
`-4
`-16
`
`F,G,H
`
`lanem u-kings
`
`M=ob, facles or lane
`
`---
`
`-~
`
`. /
`
`/
`
`: /
`
`/
`
`-- -
`- ~ l,;!> F r
`
`l ,C, N= ear mir brs at 18 25, 40, Om
`
`B.,
`
`c.,
`
`~
`
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`
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`
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`
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`
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`...........
`
`........
`
`...............
`
`"-._ "'
`
`-14
`
`-12
`
`-10
`
`-8
`
`-4
`
`-2
`
`0
`
`2
`
`4
`
`6
`
`8
`
`10
`
`12
`
`Fig. 3b - Driver's visual field mapping during road tests in motorway
`
`driving conditions. _
`
`SPATIAL FREQUENCY
`
`Fig. 3c - Example of contrast sensitivity outputs obtained from road tests.
`
`519
`
`
`
`Fig. 3d ~ Examples of calibrated visual stimuli used in road tests.
`
`The above methodology has been used for the road tests on a test car with.
`headlamps prototypes. The optical specifications for the lighting functions of
`the adapUve lighting system have been defined.
`
`Preliminary headlamps prototypes have been developed with lighting beams
`suitable for the different lighting functions (bending, motorway, country, ... ) with
`a high number degrees of freedom, this to achieve the desired light distribution.
`
`The test car equipped with such a lighting system has been used to measure
`the visual sensitivity of the driver vs:
`
`• distance and lateral position of the obstacles in the driver's visual field
`during driving task,
`
`•
`
`light beams photometric characteristics.
`
`Road tests results have been compared to the minimum value of contrast
`sensitivity requested during main driving task (lane keeping) and secondary
`driving task (signs, pedestrians, generic obstacles visibility). This value is a bit
`lower than 2.
`
`At any fixed distance of the obstacles, the field tests have been carried out in
`three different conditions:
`
`• without traffic conditions,
`
`520
`
`
`
`• with an oncoming car (in order to evaluate glare influence on oncoming
`driver's eyes),
`
`• with an incoming car (to evaluate glare influence on rear view mirrors).
`
`Measurements results in case of 40 meters distance for country driving
`In this example we can see a good
`conditions are shown in figure 3e.
`behaviour of headlamps prototypes, except in the right side of visual field
`where they are responsible for glare on right rear mirror-
`
`---e--econtrast sensitivity without oncoming
`vehicle
`.......-Jm----contrast sensitivity with oncoming vehicle
`····--•- contrast sensitivity with rear vehicle
`
`100
`
`Contrast
`sensitivity
`
`1 0
`
`...___ _____ _
`
`-----
`
`pedestrian
`
`left
`border
`lane
`
`middle
`border
`lane
`
`right
`border
`lane
`
`right
`signs
`
`Fig. 3e - Contrast sensitivity measurement results during CL driving situation in
`
`case of obstacles 4Q meters far from the driver.
`
`From these results, photometric specifications of the different lighting functions
`of the adaptive system have been defined. Figures (4a, 4b, 4c, 4d) show some
`possible final pattern configurations of the additional beams for country light
`high speed, bending and town driving.
`
`521
`
`
`
`Ver:tical angle
`
`20 1----1----+---+---+----+---+--+--t------J-----t---+--t
`15 1----1----+---+---+----+---+--+--t------J-----t--;-------;
`10 1----l---+-----,--+--+---'---+---!--+--t-----i---t-"---t---t
`5
`-~ 1-----+---+---+-----';~ :)_t:_:'.'lS'H~~~~;=?/-·): --+---t---t-----i 21. 88419
`-10 L__J__JL____J_____:sJ:i::~:±i:~~=l=t~~+----+-+--:_j
`-15 1----1----+---+---+----+---+--+--t------J,-------t---+------;
`-20 1----1----+---+---+----+---+--+--t------J-----t---+-,------;
`-50
`10
`20
`30
`40
`-40
`50
`-30
`-20
`-10
`0
`· Il.orizontal angle
`
`Joooo
`
`. 70000
`
`Fig. 4a - Country beam
`
`Vertical angle
`
`· 2 0 > - - - - -+ - - -+ - -+ - - -+ - - -+ - - - r -~+ - - t - - - - - -+ - - -+ - -+ - - -1
`i5 > - - - - -+ - - -+ - -+ - - -+ - - -+ - - - r - -+ - - t - - - - - -+ - - -+ - -+ - - - -1
`10 > - - - - -+ - - -+ - -+ - - -+ - - -+ - - - r - -+ - - t - - - - - -+ - - -+ - -+ - - -1
`l
`
`5 :L f-----+--+--+-----+'<cv~~),-,,<-?+--)--+----+---+----1 :: : :::::
`
`40 ~ fJUCOC
`-15 f-----+--+--+-----1----+---+---+--~1-----+---+--+-----1 2 _;;, UOOa.'l'
`-20 f-----+--~--+-----1----+---+---+---f----+---+--+-----l
`-50
`-40
`
`-30
`
`-20
`
`-10
`0
`10
`Horizontal angle
`
`20
`
`30
`
`40
`
`50
`
`OCUD
`
`0000
`
`Fig. 4b - High speed beam
`
`522
`
`
`
`vertical angle
`
`20 1----l---l---+---+---t---t.:..._-+--+--+--+--+----i
`15 1----1---+---+---+---t---+--+--+--+--+--+----i
`10 l - - - - l - - - t - - - t - - t - - - t - - - t - -+ - -+ - - - - t - - - - - , - - - - - t - - - t - - - 1
`
`5 -~ --~--------~~~La=L=~-~±:9~_-17.37361
`
`-10 1------t----t---t--,-----t--+-"'~==+=~~~==t'=---,-+--I
`-15 l----t--t--t---t---+--+----t-----t----t---t---t-----1
`-20 1 - - - - l - - - t - - - t - - t - - t - - t - -+ - -+ - - - - t - - - - t - - - t - - - 1
`
`-50
`
`-40
`
`-30
`
`-20
`
`10
`0
`-10
`Horizontal angle
`
`20
`
`30
`
`40
`
`50
`
`7 .00000
`
`~ :. : '
`
`2, 50000
`
`. 70000
`
`Fig. 4c - Bending beam to the right
`
`Vertical angle
`
`20 t - - - - 1 - - -+ - - -+ - - -+ - -+ - -+ - - - -+ - - -+ - - -+ - - -+ - - -+ - - - -<
`15 - - - - - - - -+ - - - -+ - - -+ - - -+ - -+ - - -+ - - -+ - - -+ - - -+ - - - -<
`10 t - -+ - - -+ - - -+ - - t - - - - - -+ - - - - - -+ - - -+ - -+ - - - - -+ - - - - -+ - - -+ - - - - - - - i
`5
`
`_ ~ ---·-~{7.;.:·:;~::_~~i~::_:--:--::~,:::~:: .. _.s:~:::e~~~:--~:::~:-;::::,:_:_:_~~bg·..,..?/,-,'J - - - -+ - - - l 15. 672 5 6
`
`-10 l----l---t---+-'-'-'--=-r-=---'+----"'-+=---+ ...... ---;..-~-----+-----1
`-15 1------+--+--+--+--+----+---+---+---+----+-----+-----j
`-20 l------+--+--+--+--+---+----+---+---+----+----1------j
`
`-50
`
`-40
`
`-30
`
`-20
`
`10
`0
`-10
`Horizontal angle
`
`20
`
`30
`
`40
`
`50
`
`.00000
`.soooo
`
`.70000
`
`Fig. 4d - Town beam
`
`523
`
`
`
`Control Strategies
`
`The impiementation of an appropriated strategy to switch from one beam to
`another is a crucial issue. The trend to implement more and more electronics
`in the vehicle leads to the po~sibility to design real time controlled lighting
`sy~tems hav,ing many input parameters for the control algorithm.
`Dynamic levelling is an integral part of the headlamp system.
`
`The switching among different lighting functions is controlled according to
`human eye capability to follow and to adapt itself to the dynamic of visual field
`illumination. In case of failure events during operation of the system recovery
`strategies are considered and implemented in the electronic control unit.
`The advc1ntages of the developed system respect to conventional ones are
`reported on table I:
`
`Tab I - ROAD1LLUMINA T/ON REQUIREMENTS FOR AN ADAPTIVE
`LIGHTING SYSTEM
`
`.
`
`.
`
`Device.s
`
`Beam
`
`patterns
`
`Visibility
`on
`
`straight
`r<>ad
`
`on ctJrve requirement
`(R150)
`[Ix]
`
`Angulc1r
`
`wihdowfor
`
`specified
`
`visibility
`
`Existing
`
`lighting
`
`systems
`
`Adaptive
`
`headlight
`
`systems
`
`Low
`
`beam
`
`High
`
`beam
`
`Country
`
`light
`
`Bending
`
`beam
`
`High
`
`speed
`
`beam
`
`58m
`
`30m
`
`40
`
`140 m
`
`120
`
`80m
`
`20
`
`vert.(-0.75°,-
`
`hciriz.(-1 °, 1 °);
`
`0.30).
`
`horiz. (-4 °, 35°);
`
`vert. (-1 ° ,-0.5°)
`
`horiz.(-1 °, 1 °);
`
`vert.(-0.3°,0°)
`
`6
`
`3
`
`200m
`
`76m
`
`524
`
`
`
`Future Developments
`
`The definition of appropriated strategies for beam switching and control is far
`· more the major issue on the evolution of intelligent lighting systems.
`The introduction of data coming from accurate navigation systems comes as a
`first logical consequence. This predictive system would make possible to
`anticipate the needed light distribution avoiding dangerous changes in the
`beam during critical driving conditions such as curves and crossing. Other
`forms of refinement of the lighting strategies could be the dependence of the
`light pattern intensity distribution on data coming from stand alone sensorial
`systems (radar and infrared night vision) that could detect problems at a farther
`distance than that allowed by the headlamp. The optical and electronic
`solutions, for the new functions presented in this paper, are only examples of
`possible technical realisations and, hence, are no longer in the industrialised
`stage. Some efforts are still necessary before their introduction in the market
`functions
`together. A gradual or partial
`functions
`for all
`especially
`industrialisation is more affordable in the medium term.
`A crucial aspect for the evolution of the front-lighting system scenario is the
`the definition of new rules and
`introduction of a new regulation comprising
`new specifications both for beam patterns and switching strategies.
`
`References
`
`1. (SAE Technical paper series 970644, 1997)
`2. (SAE Technical paper series 970646, 1997)
`3. Automotive Engineering International, October 1998, pages. 19-24
`
`525
`
`
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