Light by Laser Next Headlamp Trend, Experts Say

PARIS – The next improvement for signal lighting will be organic-light-emitting diodes, which illuminate across their whole surface and eliminate the need for lenses. The next new technology for forward lighting could be laser beams.

“Lighting…is a great challenge to all of us,” Nadine Leclair, senior vice president-engineering at Renault, says in a keynote speech to the Vision 2012 conference here sponsored by SIA, the French automotive engineering society.

“The auto maker’s challenge is to create a consistent offer for the final customer, with technology at the right time, with the right quality and at the right price.”

Osram and Philips Lighting both show OLED displays that look like, and essentially are, flat panels of plastic that light up when electric current is applied.

So far, says Osram’s Andi Konrad, OLEDs work only as flat panels, although Philips shows one that is bent slightly. Engineers and researchers are working on ways to produce OLEDs in 3-dimensional forms that would allow designers more styling freedom.

Meanwhile, Konrad says, red OLEDs are ready for industrialization and will appear as rear lighting on a vehicle within three years.

OLED rear lights, turn signals and position lights would weigh less than current technologies and would save precious packaging space. Theoretically, they could come at a lower cost with high volumes, but for the moment they are expected to arrive on less price-sensitive premium brands.

Laser lighting is next for forward lighting, according to Leclair and Jean-Paul Ravier, advanced development director-Valeo Lighting Systems, who says auto makers already are preparing such applications.

“After LEDs, there will be laser beams,” Ravier says. “It will be part of the market in the future, but LEDs will remain dominant.”

A laser could emit the headlight beams from a 0.4-in. (10-mm) slit in the front of the car, he says. The idea certainly will please designers, as many recent auto-show concepts have faces with narrow headlamp openings.

Previous lighting breakthroughs, Ravier says, have come when a new technology offered a performance improvement, new styling possibilities and a longer lifetime. Thus, halogen replaced sealed beams, xenon replaced halogen and LEDs are coming as the next wave.

In each case, the cost of the new technology, at least at first, was higher than what it replaced.

Laser headlamps would offer better performance and new styling features, Ravier says, but LEDs already have a longer lifespan than required. The strength of LEDs is that they already are competitive with xenon high-intensity-discharge lamps and will become less costly in the years ahead.

“We can forecast a quick replacement of HID in the next three years and a more progressive replacement of halogen in the next 10 years,” he writes in the paper delivered at the conference.

“LEDs will be used intensively for mass markets, becoming the dominant source, but laser beams will be introduced for premium cars, as it is often the case for new technologies, where performance and style are much more important than costs.”

Systems using laser diodes would put more light on the road in very interesting ways.

Employing a layer of phosphor where several blue laser beams intersect, a secondary white light can be created with a potential for luminance about five times greater than the best current LED headlamps, Ravier says.

“Used in automotive applications,” he writes, “this high luminance source can allow new functions such as picture beam, or lighting systems with very compact output for very thin styling requests.”

Lasers already are used at concerts, for example, to project images on a wall. Fast-moving microelectronic-mechanical systems make a pattern appear fixed, although it is a light beam moving very fast. Thus, lasers could shine around the corner, automatically dim so as not to glare on an oncoming car and produce both low and high beams.

Lasers could handle more complex functions through:

Improvements in LEDs mean Valeo now can produce a good low beam with a 0.8-in. (20-mm) lens or reflector, and a high beam with a 1.6-in. (40-mm) element. But with the extra luminance of a laser, Ravier says, “a very thin lighting system only 10 mm high is possible, allowing new styling approaches.”

To make the idea a reality requires work on thermal properties, which now limit laser lifetime to 3,000-10,000 hours, he says.

In addition, Ravier says, “auto is very demanding for color shifts with temperature, and the wavelength from the laser diodes changes with temperature, which will have to be taken into account in the design.”

While laser diodes are more efficient electrically at their natural blue-light level, they are less efficient than LEDs when white light is made through the phosphor transition, producing only 40 lumens per watt vs. 95 lumens per watt with the best LEDs.

And cost is a barrier, being at the moment about 10 times more expensive than an LED system. However, Ravier says, “Initially this will not prevent introduction of laser technology, if services can be demonstrated.”