By Paul-Henri Matha
At the 2018 Geneva Motor show seven years back, the Mercedes Maybach was the first car equipped with high-definition (HD) headlamps. Then Audi launched their e-tron with HD lamps. Both these pioneering cars had lamps made by Marelli.
HD headlamps are those with over 1,000 pixels, or a resolution finer than 0.1°. Before HD technology, the maximum resolution for ADB was around 1 degree, achieved with solutions like single-row matrix or multi-row pixel.

With HD technology, the resolution can be made much finer, with two major goals: increase safety in ADB mode by making the shadows smaller and more precisely aligned with other road users’ eyes, and the ability to project symbols or text on the ground and on the wall.


DLP Technology
This technology was initially possible with DLP technology from Texas Instruments, already known for consumer applications (projectors). The first automotive DLP module was developed by Marelli for Mercedes and Audi, and got the Automotive News Pace award in 2020.

It was quite large—183 mm deep.

With a 0.55-inch, 1.3-megapixel DMD chip, the possible HD area was 14°H × 7°V. Imax was 50 kcd. The rest of the low and high beams were produced by a second module, such as a bi-matrix, to reach the width and hight requirements of the beam patterns.

Legalities
From January 2023, after around five years of discussion in GTB and GRE, UN R149 was updated with the 01 series of amendments to include four road projection symbols. These projections must be just below the low-beam cutoff, at or below 1.2 degrees down from horizontal.
So, if the headlamp is at 80 cm height, road projections can be seen at 8 m from the car, as shown by BYD during DVN Shanghai 2024 (here at 5° down from H):


Relevant section of UN R149-01
At GRE in October 2024, it was decided to add the predicted-trajectory symbol soon:

In China, from 1 July 2025, all road projections—considered part of ADB—will be accepted under the new Chinese national standard GB4599-2024, without a restricted list of symbols as in UN R149.
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