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Overview
• History• Regulations• Forward illumination
– Head lamps
• Signaling devices– Turn signals– Hazard flashers– Stop lamps (Brake lamps)
• Other light applications in traffic– Adaptive lighting– Traffic lights
History
1880 Carbide lamps
1898 1st electric head lamps on the Columbia Electric Car
1912 Electrical ignition and lighting system by Cadillac
1924 Bilux bulb (dipped and main light from one bulb)
1940 Sealed beam headlamp (US, GB, J)
1962 1st halogen head lamp (Europe)
1991 High intensity discharge system
2001 LED brake lights
2007 LEDs in front lighting
Regulations
• Two standards for beam pattern and headlamp construction
• ECE standard– Industrialized countries except US
• SAE standard– US
• Differences in the– permitted amount of glare (SAE permits more glare)– minimum amount of light required to be thrown straight down the
road (ECE requires less)– specific locations within the beam at which minimum and
maximum light levels are specified
Forward Illumination – Head Lamps
Reflection type Projection typeParabolic Free Form (FF) Ellipsoidal (DE) Super DE with FF
Side view
Top view
Pictures: http://hella2.co.nz/
Forward Illumination: Head Lamps
Light sources – state of the art
Tungsten-halogen High intensity discharge (HID)- Tungsten filament- Heating by electrical
power and emission of light (black body)
- Halogens included for chemical transport (tungsten back to the electrode – longer life)
- Lifetime H7 450 h
- Electric arc of incoupling the energy
- Metal halides evaporate and form a plasma
- Xenon for quick start- High luminous flux- Lifetime 2000 h- Blue light is scattered by
fog and rain or snow
Forward Illumination – Next Generation
Light emitting diodes (LED)• Daytime
runninglight
• Fog lights
• LED head-lamp prototype
Forward Illumination – Next Generation
• Light emitting diodes (LED)• Depending on the wanted color: LED chip or LED-chip +
phosphor• Direct transformation of electricity into light• Advantages
– High efficiency– Long lifetime (up to 10.000 h)– Resistant against vibrations
• Disadvantages– Temperature dependent light output– Cost intensive temperature
management is necessary– Cold front end of the light
system – danger by ice and snow
Signaling devices: Turn signals
Turn signals / hazard flashes• Commonly driven by
incandescent light bulbs
• New development uses LED technology
Signaling devices: Brake lamps
• Espacially at high speed immediate reaction is necessary
• LED with shorter time between activation and visible light output then incandescent light bulbs– At a speed of 100 km/h this can result in a reduction of the
braking distance of 5,5 m under comparable conditions.
• LEDs available in some cars, e.g. Audi A6 and A8• Emergency braking display (flashing, higher light output
or bigger illuminated area in case of severe braking)• 3rd brake lamp: Centre High Mount Stop Lamp (often
LED array)
Other Applications
• Traffic lights (LED with higher light output,longer lifetime and less power consumption)
• Adaptive lighting (automatic control of the illuminated area in curves, …)