retroreflective material could help autonomous vehicles read traffic signs | Technological impetus

Research at the University of Buffalo explored the science behind micro-scale concave interfaces (MCIs) – structures that reflect light to produce beautiful and potentially useful optical phenomena. In a published paper, Buffalo engineering researcher Qiaoqiang Gan defined how light interacts with concave micro-scale interfaces. Future applications of the technology, he said, could include helping autonomous vehicles to recognize traffic signs.

The study focused on a retroreflective material – a thin film made up of polymer microspheres deposited on the sticky side of a transparent tape. The microspheres are partially embedded in adhesive tape and the protruding parts form MCIs.


Concentric rainbows are produced when white light is reflected from concave micro-scale interfaces. Courtesy of Jacob Rada, University of Buffalo.


When white light shines on the film, it is reflected in such a way that the light creates concentric rainbow rings, the team said. Alternatively, a single color laser will generate a pattern of bright and dark rings. Reflections from infrared lasers also produced distinctive signals made up of concentric rings.

To test the technology, the team applied the thin film to a stop sign. The patterns formed by the material appeared clearly on both a visual camera that detects visible light and a lidar camera that detects infrared signals, Jacob Rada, co-first author and Ph.D. student at the University of Buffalo, said.

“Currently, autopilot systems face many challenges in recognizing traffic signs, especially in real-world conditions,” Gan said. “Smart traffic signs made from our material could provide more signals for future systems that jointly use lidar and visible pattern recognition to identify important traffic signs. This can be useful for improving the road safety of self-driving cars. ”

Visible (left) and infrared (right) images of a panel created using micro-scale concave interfaces to form the word STOP and other elements.  The infrared image was taken using a lidar camera.  Courtesy of Jacob Rada, University of Buffalo.


Visible (left) and infrared (right) images of a panel created using micro-scale concave interfaces to form the word STOP and other elements. The infrared image was taken using a lidar camera. Courtesy of Jacob Rada, University of Buffalo.


The team demonstrated a combined strategy to improve the lidar signal and visible pattern recognition currently performed by visible and infrared cameras, Rada said. “Our work has shown that the MCI is an ideal target for lidar cameras, due to the consistently strong signals that are produced. ”

A US patent for the material has been issued, as has a patent in China, with Fudan University and the University of Buffalo as patent holders.

According to Gan, future plans include testing the film using different wavelengths of light and different materials for the microspheres, with the goal of improving performance for possible applications such as traffic signs designed for future systems. autonomous.

The research was conducted by the University of Buffalo, Shanghai University for Science and Technology, Fudan University, Texas Tech University, and the University of Hubei. The work was partially funded by a grant from the US National Science Foundation.

The research was published in Materials applied today (www.doi.org/10.1016/j.apmt.2021.101146).

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