Lecture „Incoherent Light Sources“ Summer term 2007 ... · Forward Illumination: Head Lamps Light sources – state of the art Tungsten-halogen High intensity discharge (HID)

Automotive lighting

Lecture „Incoherent Light Sources“Summer term 2007Stephanie Möller

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, …)

Thank you for your attention!