Digital light: a new light model that goes far beyond illumination

Throughout human history, flames have been the main way for people to generate light. As technology advances, people discover that metal elements in light bulbs can also emit effective light at ultra-high temperatures, but this technology was later replaced by LEDs.

These different forms of light sources have one thing in common: they are all single light sources that can project a relatively uniform light beam over a wide range of illumination. This also greatly limits the flexibility of beam direction control. Compared with traditional light sources, LED lamps perform better in beam control, but even with the help of lenses or reflectors, the adjustment of LED beams is still limited.

Thanks to a series of innovations in design and manufacturing by ams and osram, lighting technology has ushered in a historic turning point. Researchers have successfully developed a light source array composed of extremely tiny LEDs, which are only one tenth the diameter of a human hair. This technological breakthrough has created a completely new way of lighting: it abandons the traditional block or beam-shaped light-emitting mode and adopts a matrix composed of thousands or even millions of tiny point light sources (i.e. pixels). Each point light source is precisely controlled by a digital data stream, which can achieve dynamic reconstruction of the matrix light output in milliseconds.

This new mode of light emission forms the basis for a new concept we call “digital light”.

Figure: The use of high-resolution projection technology enables smart lighting to improve the safety of our daily lives

This idea can be traced back to 20 years ago: using a new type of LED chip composed of a micron-sized light point array to create a high-resolution projection light source. However, in order to subdivide the semiconductor area of ​​a traditional square millimeter-sized LED chip into thousands of light pixel matrices of only a few microns in size, a series of technological breakthroughs are required in many fields such as basic physics, semiconductor manufacturing and materials science.

In addition, ams has developed a new chip architecture and pixel-level bonding technology to ensure the connection between each LED pixel and its driver within a single integrated device. It is the integration of these innovative technologies that has enabled ams to successfully realize the concept of a monolithic micro-LED array (see Figure 2 below).

The technology is now in mass production. The first LED pixel arrays from ams-OSRAM are being used in an innovative adaptive high beam (ADB) automotive headlight system, EVIYOS®. Automakers are the first commercial customers of the EVIYOS® chip and are working on advanced headlight designs with 240x80 pixel arrays of individually controllable LED pixels. The application of this digital light technology will have a profound impact on driving safety, night driving experience, and provide drivers and other road users with a new way of signaling.

Pixel-by-pixel digital control technology enables headlights to operate safely in permanent high-beam mode. With the help of cameras to capture the position information of road users such as oncoming vehicles and pedestrians on the roadside, EVIYOS® headlights can accurately turn off pixels that cause glare while ensuring the maximum lighting range to clearly illuminate the road ahead for the driver. The system dynamically adjusts pixel control at millisecond speeds to achieve the widest and farthest beam projection without affecting the sight of other road users. This innovative technology significantly improves the driver's driving comfort and builds a solid safety line for all road users (see the figure below).

Figure: Anti-glare design: improving overall safety

EVIYOS® LED headlights also have the ability to project information onto the road. For example, micro LED headlights can project indicator lines to clearly mark the road area that the vehicle is about to occupy: the headlights can prompt the driver whether the vehicle can pass through a narrow space, or provide driving guidance for the driver in complex road conditions (such as temporary road construction areas).

The potential of digital light technology goes far beyond lighting. For example, micro-LED pixels are small enough to be embedded in transparent displays while still keeping the image clear and sharp. The initial application of this transparent display technology may be seen in the rear window of a car, used to display signals and warning information to the vehicles behind.

The transparency of micro-LED displays comes from the wide spacing between its micron-sized light points - in a high-resolution TV, the RGB micro-LED array may occupy as little as 0.5% of the total display area. The large gaps between these micro-LEDs also provide space for adding other microscopic components, such as distributed cameras or infrared sensors, turning it into a multi-functional display with functions such as gesture sensing and proximity detection.

Micro pixel arrays, with their extremely small pixel size, have become a core component of the next generation of augmented reality (AR) and virtual reality (VR) devices. Taking smart glasses as an example, micro LED displays can be embedded in the device as micro projectors to overlay AR information into the user's field of view in a non-invasive manner. Proof-of-concept studies have shown that a single pixel array can embed more than 2 million independently addressable LED pixels, and each pixel has a side length of only about 1 micron, thus presenting full HD resolution images to smart glasses users (see the figure below).

Figure: Looking into the future: high-definition images directly visible

In addition to the above-mentioned projection systems, digital light has also shown new value in many other applications. For example, 3D printers will be able to achieve ultra-high precision curing, thereby building more precise and complex structures.

In the field of artificial intelligence (AI) application data centers, the use of digital light technology is expected to significantly improve the efficiency of high-bandwidth optical communications. Currently, high-speed optical communication links mainly rely on high-frequency switching laser light sources to transmit serial data streams through fiber optic cables. Micro-LED array technology - in which the LED pixel size is hundreds of times smaller than the laser light source - shows great potential for parallel transmission of data. This innovative technology will greatly improve bandwidth efficiency and help reduce energy consumption in high-energy-consuming data centers.

Developing a light source made of individually addressable pixels has required a huge effort, but ams and OSRAM have worked together with industrial partners such as the Fraunhofer Institute for Reliability and Microintegration (IZM) in Berlin over the past decade, and with funding from governments and the European Union, to achieve this technological breakthrough.

The vision of flexible, digitally addressable light sources is also inseparable from the accumulation of a series of technological innovations. This optical technology is a completely innovative scientific research result, and its potential application prospects are yet to be explored and imagined. The first application case, the adaptive high beam (ADB) system, will completely change the night driving experience. This is just the beginning of the value creation of micro LED arrays, and its application potential will be even broader in the future.

By bringing together many talented people and combining industrial and scientific forces to achieve major technological breakthroughs, we are able to open up new horizons in products in multiple market sectors such as industrial, consumer, and automotive. This exciting achievement is another new chapter in the history of ams and OSRAM.

As a company with a long history, ams OSRAM has repeatedly made revolutionary advances in important product categories: digital light technology is the latest in this series of innovations.

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Dr. Norwin von Malm
AMS OSRAM
Senior Director of New Technologies

Since 2003, Norwin has held various positions in R&D at OSRAM. He successfully developed thermal processes, material stacks for organic light-emitting diodes (OLEDs) and developed the first multi-pixel InGaN and InGaAlP light-emitting diodes (LEDs). In his role as LED chip research manager, he drove the µAFS project from an R&D perspective. After leading back-end material development, Norwin currently heads the New Technologies department. The department focuses on finding new front-end ideas and technology concepts in the scientific and startup world and evaluating them for future use in the company's products.

Stefan Groetsch Director of System Solutions Engineering at ams OSRAM

Stefan currently works as a Hardware/Software Team Leader in the Engineering Department at OSRAM Mobile System Solutions. Since 1995, he has accumulated a wide range of professional experience, including senior principal engineer in the application field, EVIYOS® system architect, FMER project coordinator for the µAFS project, application engineer and R&D project and platform manager for OSTAR power LEDs and power laser diodes in video projection and automotive headlights.