Can a man-made device “see?” That answer may literally be in the eye of the beholder and close to a reality as a cutting-edge artificial electronic retina can already mirror the dynamics and functionality of human sight to an uncanny degree. It’s made possible by perovskites, a thin-film material that can absorb light and transport electric charges with remarkable speed and efficiency. Developed for use in solar cells, the material could also help restore vision for people.
Seeking to improve applications for computer vision, researchers at the King Abdullah University of Science and Technology (KAUST) have developed a neuromorphic vision system that can perform functions that were once the sole purview of the human eye; the system can “see” handwritten numbers. How does it work? Similar to the way rod retina cells in the human eye function, a matrix of photoreceptors changes its capacitance in response to light. This photoreceptor array can be “read” by a CMOS sensor as data, effectively converting photons into data to be processed by an artificial neural network. The system gets handwritten numbers right about 70% of the time.
Can’t today’s camera technology already do something similar? Yes, but the current camera systems consume a lot of energy in doing so. By contrast, a neuromorphic vision system uses far less energy and has the potential for exponentially faster processing speeds compared with current camera technology. Plus, the artificial retina created by KAUST researchers shows more promise in mimicking human sight. In a test using LED illumination and a 4X4 array of photoreceptors, responses to visible colors closely mirrored those of the human eye.
Much of the new system’s success can be attributed to a hybrid material made up of perovskite nanocrystals, which have garnered the interest of solar-cell researchers for their considerable ability to absorb a wide spectrum of light, as well as their affordability. KAUST researcher Mani Teja Vijjapu explains, “We chose hybrid perovskites because of their exceptional photoelectronic properties, such as excellent light absorption, long carrier lifetime, and high carrier mobility.”
But reading handwritten numbers is not just a party trick; artificial retinas have the potential for important real-world applications. Will we see them replacing eyes in humans through transplants? While visual prosthesis applications could be on the horizon, we’re not there yet. For now, perovskite systems can serve as fast, energy-saving alternatives to current systems with photodetectors; the team at KAUST has its sights set on advancing the vision systems of robots and cameras.
