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Holographic ground projector lets autonomous cars communicate with pedestrians

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The 3D rendering shows a possible application involving the holographic ground projector (Credit: Fraunhofer IOF)
The 3D rendering shows a possible application involving the holographic ground projector (Credit: Fraunhofer IOF)

A new holographic projector system will allow autonomous cars to communicate with pedestrians and cyclists without the need for hand signals from a human driver, according to its creators.

Developed by a team at the Fraunhofer Institute for Applied Optics and Precision Engineering in Jena, Germany, the projector system was built as part of the Mamek project, also involving partners including Audi.

“Imagine a situation in which a cyclist isn’t sure whether an approaching car is giving way or not – but then a bright projection appears in front of the vehicle, indicating that it has detected the bike and is waiting for it,” the Fraunhofer announcement said. “This is one example of how cars and humans might communicate with one another on the streets of the future.”

Two technological approaches are being explored – displays shown directly on the car itself, and holographic projections on the ground surrounding the vehicle. The Fraunhofer team is working on the latter.

“Many cars already feature LED-based symbol projection systems that project images onto the ground when the driver gets out. But they’re not bright enough yet for daylight conditions, and the images they produce are static, so they’re not suitable for enabling autonomous cars to communicate with their environment,” said researcher Norbert Danz.

The challenge was therefore creating an ‘ultra-bright’ projection that is visible even in sunlight and can display information dynamically. It also has to illuminate a sufficiently large area, to cover all directions around the car with just a few projectors.

The Fraunhofer team used state-of-the-art laser technology to create their dynamic micro-projector. Four laser diodes illuminate an image generator known as a spatial light modulator (SLM), which distributes the light in a way that forms a particular image on the road. To achieve the right level of brightness and ensure that the projection area is as large as possible, the system generates four ‘sub-images’ that are then merged into one.

“As the projector is very near to the ground and the projection angle is very wide, it’s difficult to create one large image, so instead we distribute the image across multiple laser diodes and widen each individual image using micro-optic telescopes.

“Additionally, the direction of projection is determined by an array of microprisms, allowing us to achieve a projection area of 100x30cm at a distance of less than 50cm,” said Danz.

With dimensions of just 7x7x5cm, the system could be integrated under the doors on ‘any’ car, the researchers claimed. Installing multiple projectors makes it possible to display pictograms on the road all the way around the vehicle, while the modular architecture opens up the possibility of depicting dynamic elements.

The brightness level of 10,000 lux, depending on image, should allow cyclists and pedestrians to see projections even on a sunny day, the announcement said.

The SLM image generator was provided by Berlin company Holoeye Photonics, one of the project partners, and Thuringia firm Docter Optics SE was also involved in the construction of the projectors.

The system developed as part of the Mamek project is now being integrated into a demonstration vehicle and networked with appropriate sensors from a highly semi-autonomous vehicle. 

The researchers will exhibit a laboratory demonstration model of the micro-projector at Laser World of Photonics in Munich, 27-30 June.

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Content published by Professional Engineering does not necessarily represent the views of the Institution of Mechanical Engineers.


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