Like I wrote in my precedent editorial, I discovered on the new Mercedes CLS stunning LED headlights better than Xenon . I was impressed by both the quantity and the quality of this light.
For the quality of light, distribution, homogeneity, smoothness of movement, lighting designers acheived a wonderful job.
For the quantity, it is mainly depending of the light output of the LED light sources.
It is a simple question of calculation. With good Xenon light, the flux on the road is between 900Lm and 1,100Lm. So to have better light than Xenon, we need to have more than 1,100Lm on the road.
If we consider:
1) A LED chip to-day emits of around 150Lm.
2) Only 50% of the light arrives on the road (some lighting suppliers announce 60% with LED vs 35% with Xenon).
It means that if we want to have more than 1,100Lm on the road, we need 2,200Lm from the light sources and therefore we need 2,200Lm/150lm = 15 LED chips.
So in order to beat Xenon as far as quantity of light is concerned, more than 15 current LEDs have to be packed together for the low beam or 4 LED modules (of 4 chips each) as used in Mercedes CLS and Audi A7.
So lighting players proved that the LED technology may provide more light on the road than Xenon.
What about the cost? The CLS headlamp emphasizes 2 reasons which explain such a high cost:
1)Technical reasons with Thermal, electronics, optics, assembling challenges.
2) Styling differentiation.
The first reason will soften with the progress of LED technology and new headlamp designs.
The 2nd reason will subsist because styling differentiation is expensive work.
In conclusion, making better light than Xenon is now possible but we have a long uphill climb to have better light with lower cost.