The Rainbow Technology could help Independent Vehicles Interpret Signs

By reflecting different wavelengths of light, the high-tech reflective film would make signs more visible to self-driving cars. A new study delves into the science of microscale concave interfaces (MCI), which are structures that reflect light to create beautiful and potentially useful optical phenomena. According to the researchers, future applications of these effects could include assisting autonomous vehicles in recognizing traffic signs. There are several images available, including one of a sign made from the material.

“Before you try to implement a technology, you must be able to explain how it works to someone else. Our new paper describes the interactions of light with microscale concave interfaces “Qiaoqiang Gan, an engineering researcher at the University of Buffalo, notes that future applications of these effects could include assisting autonomous vehicles in recognizing traffic signs.

Microscopic reflective materials on road signs may one day enable self-driving cars to electronically “read” road signs. The study was published online in Applied Materials Today and will be featured in the September issue.

Microscopic reflective materials on road signs may allow self-driving cars of the future to electronically “read” road signs. A new study explains the science behind microscale concave interfaces (MCI); structures that reflect light to produce beautiful and potentially useful optical phenomena.

Gan, Ph.D., professor of electrical engineering in the UB School of Engineering and Applied Sciences, led the collaborative study, which was carried out by a team of researchers from UB, the University of Shanghai for Science and Technology, Fudan University, Texas Tech University, and Hubei University. Jacob Rada, a UB Ph.D. student in electrical engineering, and Haifeng Hu, Ph.D., a professor of optical-electrical and computer engineering at the University of Shanghai for Science and Technology, are the first authors.

“Smart traffic signs made from our material could provide more signals for future systems that identify important traffic signs by combining LIDAR [laser imaging, detection, and ranging technology] and visible pattern recognition. This could help improve traffic safety for self-driving cars, according to Qiaoqiang Gan, a professor of electrical engineering at the University at Buffalo.

Reflections that form concentric rings of light

The research focuses on a retroreflective material, which is a thin film made up of polymer microspheres laid down on the sticky side of a transparent tape. The microspheres are partially embedded in tape, with the protruding parts forming MCIs.

This rainbow-making tech could help autonomous vehicles read signs

According to the new paper, the white light shining on this film is reflected in such a way that it creates concentric rainbow rings. Alternatively, striking the material with a single-colored laser (in this case, red, green, or blue) produces a pattern of bright and dark rings. Infrared laser reflections also produced distinct signals consisting of concentric rings.

The study goes into great detail about these effects and reports on experiments that used the thin film in a stop sign. According to Rada, the co-first author from UB, the patterns formed by the material were clearly visible on both a visual camera that detects visible light and a LIDAR (laser imaging, detection, and ranging) camera that detects infrared signals.

“Right now, autopilot systems face numerous challenges in recognizing traffic signs, particularly in real-world conditions,” Gan says. “Smart traffic signs made of our material could provide more signals for future systems that identify important traffic signs by combining LIDAR and visible pattern recognition. This could help improve traffic safety for self-driving cars.”

“We demonstrated a new combined strategy to improve LIDAR signal and visible pattern recognition, which is currently performed by both visible and infrared cameras,” Rada says. “Our research demonstrated that the MCI is an ideal target for LIDAR cameras due to the consistently strong signals produced.”

A US patent for the retroreflective material has been issued, as has a Chinese counterpart, with Fudan University and UB as the patent holders. The technology is now available for purchase. Gan says that future plans include testing the film with different light wavelengths and microsphere materials, with the goal of improving performance for possible applications such as traffic signs designed for future autonomous systems.

“We demonstrated a new combined strategy to improve the LIDAR signal and visible pattern recognition that are currently performed by both visible and infrared cameras,” said University of Buffalo researcher and co-author Jacob Rada. “Our research demonstrated that the MCI is an ideal target for LIDAR cameras due to the consistently strong signals produced.”

While the autonomous vehicle market is still in its early stages, it is expected to begin making its presence known on public roads in the not-too-distant future. “Autonomous vehicles capable of operating without a driver may be commercially available and legal to use in some jurisdictions by the late 2020s, but will initially have high costs and limited performance,” according to a recent Victoria Transport Policy Institute report.