How ingenuity and expertise led to the development of our multi-pixel LED

The origin of a technology breakthrough often lies not in a scientific or engineering insight, but in a vision, an imagined future. For a specialist team of our engineers in the early 2010s, the spark for their imagination came from a discussion with a customer. Their wild idea? A pixelated LED light source.

At the time, an LED was a simple chip producing one homogeneous light beam - that is, a single 'pixel'. What our engineers were thinking of was a truly futuristic idea for a beam made up of hundreds or thousands of individual beams. Applied in headlights, this idea had the potential to give light a new meaning: a beam that can adapt dynamically to changing conditions outside the car, and as well, a beam that can convey messages.

Soon, the potential value of this idea for industry and for the end consumer became so appealing that a small but dedicated development group was set up, drawing on participants from across the whole value chain, from the LED manufacturer, to a headlamp manufacturer and a car OEM.

This pioneering vision led eventually to the introduction in 2023 of ams OSRAM's EVIYOS® technology.
The EVIYOS® LED is a multi-pixel light source for car headlamps which can project pictures on the road, and selectively dim sections of the high beam to avoid dazzling other road users while illuminating much more of the driver's field of view than a conventional low-beam headlamp does.

The scale of the technological hurdles that had to be overcome was enormous. When the work started, a single LED was a chip with a typical light-emitting area of up to 1mm x 1mm. The dimensions were far too large to fit the concept of a 'multi-pixel' headlamp.

But the problem did not stop with the need for smaller LED light sources: a multi-pixel headlamp would also require new electronics for controlling the beam, and new packaging and manufacturing technologies for making the system. It was almost impossible to imagine how such a product could be made. The seed, however, had been planted.

In fact, the sheer apparent impossibility of the problem forced the engineers to consider solutions that normally might have been rejected out of hand as being too extreme or risky or unlikely to succeed. The development work started with a 4-pixel LED as a proof-of-concept. But this did not reflect our team's vision: their idea was to make a headlamp which contained thousands of pixels.

There was a huge gulf between the four pixels in the proof-of-concept, and the multi-pixel headlamp that the team had in mind. How could it justify the enormous development effort and risk required to bridge the gap between four and thousands of pixels?

In fact, market demand was beginning to move in the team's favor. The first adaptive driving beam (ADB) headlamps with 20 mm x 1mm chips on the OSRAM OSTAR headlamp platform were coming on the road, starting in a luxury car and extend to compact cars thanks to the improved safety they offered for night time driving.

But it was obvious that those ADB solutions with single LED chips would reach a physical limit at around 100 chips. To realize the original team's vision, tens of thousands of pixels were needed: to fill the gap, it was clear a completely new technology was needed.

This moment brought an offer from the German government for a publicly funded project. This gave the opportunity to form a consortium of industrial and scientific contributors:

• Daimler, the car OEM, which could define the system requirements and provide the application environment for testing and validating the headlamp
• Hella for designing and assembling the lamp
• OSRAM* for the LED, and for integration of the LED with an IC and associated electronics
• Infineon, to make an LED driver capable of controlling multiple LED 'pixels'
• Fraunhofer for technology system integration

As the µAFS (Micro Advanced Frontlighting System) project team, the engineers from these companies worked from 2013 to 2016. OSRAM, developing the opto-semiconductor technology, encountered many problems in realizing its ambitious microLED concept, including:

• Producing sufficient optical power output (brightness) from the LED
• Crosstalk at the LED and phosphor layer, causing light to leak between LED pixels
• Difficulty in maintaining color consistency across the microLED array

Nevertheless, the teams found solutions, and in 2016 revealed the fruit of their labor: a 1,024-pixel microLED headlamp concept that was able to individually control each pixel. This was an astonishing feat of engineering, producing far smaller LED point light sources than had ever been made before. In fact, this demonstration design contained 10 times more LED pixels than any existing technology could support, which led to the development of the EVIYOS® 1.0.

The moment of revelation - the release of the EVIYOS® 1.0 - was, however, both a triumph and a crushing disappointment. To make a real headlamp from this pixelated LED, headlamp makers would require as many as five of the multi-pixel LEDs, each with its own optics. It became clear that this would be too cumbersome and expensive to manufacture. Despite all the valuable engineering breakthroughs that the OSRAM team had made, their proof-of-concept was not the basis of a commercially viable product.

It was back to the drawing board for the team. And the task was now even harder, because the car industry had decided that its idea of dynamic forward lighting included the ability to project pictograms (such as safety warning or information messages) on to the road. This would require even more pixels.

Despite the µAFS disappointment the OSRAM team never lost hope. In fact, they were in 2018 buoyed by the news that two large competitors in the LED market had learned from the papers published by the µAFS project team, and were now busy attempting to develop their own automotive microLED projectors. The race was on!

So now, two years after finishing the µAFS consortium it was decision time for OSRAM: it faced the choice of walking away, or doubling down on its investment in the technology.

OSRAM had always been a leader in the technology of light. It had a famous history of innovations in automotive lighting. Breakthroughs in opto semiconductor technology had always required courage and perseverance, and the multi-pixel LED was no different. So OSRAM committed itself to the technology: with a substantially larger team, drawing in experts from multiple disciplines, now started work on developing a commercially viable product. After becoming ams OSRAM as the result of the merger between OSRAM and analog semiconductor manufacturer ams, the team also benefited from the Austrian company's in-house IC design and manufacturing expertise.

It took another five years of relentless research and development to produce the new EVIYOS® LED. By 2023, ams OSRAM was ready to launch the EVIYOS® product: a 25,600-pixel LED in a single package with a fully integrated driver IC which individually controls every single pixel. The EVIYOS® LED fully realizes the original vision for multi-pixel LED technology: the beam can be precisely controlled to cut off the beam where it would dazzle the occupants of oncoming vehicles or pedestrians by the side of the road, while providing a large, bright field of illumination to light the road ahead even better than a conventional high beam does.

Dedication:

Stefan Grötsch

published on April 23, 2024

Stefan is head of the hardware/software team in the OS Mobility System Solution Engineering division. Since 1995, he has worked as a Senior Principal Engineer in the field of applications, as a system architect for EVIYOS®, as the FMER-Project Coordinator for the µAFS-Project, as application engineer and R&D project and platform manager for OSTAR Power LEDs in Video Projection and Automotive Headlamps and Power Laser Diodes.

Joachim Reill

published on April 23, 2024

Joachim started in 1996 with development of telecommunication lasers for fiber optic solution. Over the time he worked in the area´s of automotive, general lighting, consumer, industry and was taking care on project management of 1st Headlamp LED (OSTAR Headlamp) and the beginning of EVIYOS® 2.0 program and serves now as global lead for System Solution Engineering for Mobility and Illumination.