A hemispherical-shaped digital camera that mimics the design of ocular systems found in arthropods offers a wide-angle bug’s-eye view and nearly infinite depth of field for applications ranging from advanced surveillance cameras to miniaturized endoscopes. Insects have unique compound eyes that comprise arrays of smaller eyes acting together to provide image perception. Each small eye, known as an ommatidium, is made up of a corneal lens, a crystalline cone and a light-sensitive organ at the base. The entire system is configured to provide exceptional imaging properties, many of which lie beyond the reach of existing man-made cameras. Taking cues from Mother Nature, an interdisciplinary team of researchers, led by John A. Rogers of the University of Illinois at Urbana-Champaign, developed a technique to build cameras made up of flexible, large arrays of tiny focusing lenses and miniaturized detectors in an almost-hemispherical layout, similar to eyes found in insects such as fire ants, bark beetles, bees and dragonflies. The technology provides a wide-angle field of view, low aberrations, high acuity of motion and high depth perception. The new digital cameras developed at the University of Illinois at Urbana-Champaign exploit large arrays of tiny focusing lenses and miniaturized detectors in hemispherical layouts, just like eyes found in arthropods. Courtesy of John A. Rogers, University of Illinois at Urbana-Champaign. “Full 180-degree fields of view with zero aberrations can only be accomplished with image sensors that adopt hemispherical layouts — much different than the planar CCD chips found in commercial cameras,” said Rogers, Swanlund Chair Professor at the university. “When implemented with large arrays of microlenses, each of which couples to an individual photodiode, this type of hemispherical design provides unmatched field of view and other powerful capabilities in imaging. Nature has developed and refined these concepts over the course of billions of years of evolution.” Building these systems represents a daunting task because existing camera technologies rely on bulk glass lenses and detectors constructed on the planar surfaces of silicon wafers, which cannot be bent or flexed, much less formed into a hemispherical shape. “A critical feature of our fly’s eye cameras is that they incorporate integrated microlenses, photodetectors and electronics on hemispherically curved surfaces,” said Jianliang Xiao, an assistant professor of mechanical engineering at the University of Colorado at Boulder and co-author of the study. “To realize this outcome, we used soft, rubbery optics bonded to detectors/electronics in mesh layouts that can be stretched and deformed, reversibly and without damage.” The digital camera exploits large arrays of tiny focusing lenses and miniaturized detectors in hemispherical layouts, just like eyes found in arthropods. Full 180 degree fields of view with zero aberrations can only be accomplished with image sensors that adopt hemispherical layouts. Courtesy of John A. Rogers, University of Illinois at Urbana-Champaign. The camera’s electronics, detectors and lens arrays are first formed on flat surfaces using advanced techniques adapted from the semiconductor industry, said Xiao, who began working on the project as a postdoctoral researcher in Rogers’ lab. Next, the lens sheet — made from a polymer material similar to a contact lens — and the electronics and detectors are aligned and bonded together. Lastly, the investigators applied pneumatic pressure to deform the system into the desired hemispherical shape. This process is akin to blowing up a balloon, but with precision engineering control. The individual components are coupled together to avoid movement during this deformation process. Here, the spaces between the artificial ommatidia stretch to accommodate the geometry transformation from planar to hemispherical. The electrical interconnections are thin and narrow, in filamentary serpentine shapes; they deform as tiny springs during the stretching process. According to the researchers, each microlens produces a small image of an object with a form dictated by the parameters of the lens and the viewing angle. An individual detector responds only if a portion of the image formed by the associated microlens overlaps the active area. Images acquired from the stimulated detectors are reconstructed using models of the optics. The camera also can adapt to different light levels using software algorithms and data acquisition systems. A digital camera with a hemispherical compound design inspired by eyes found in the insect world. The resolution of the device shown here is comparable to that of a common fire ant. The system incorporates an array of rubber microlenses and silicon photodetectors in a thin, stretchable sheet that can be inflated like a balloon to form the final hemispherical shape. Courtesy of the University of Illinois and Beckman Institute. Over the past several years, Rogers and colleagues have developed new classes of electronics that can bend, twist and stretch like a rubber band for a variety of fields ranging from photovoltaics, to health/wellness monitors, to advanced surgical tools and digital cameras with designs of the mammalian eye. (See: Stretchable Electronics — Good for the Heart and Stretchable Electronics) “Ever since, we have been intrigued by the possibility of creating digital fly's eye cameras,” Rogers said. “Such devices are of longstanding interest, not only to us but many others as well, owing to their potential for use in surveillance devices, tools for endoscopy and other applications where these insect-inspired designs provide unique capabilities.” Additional institutions involved in the study include Northwestern and Harvard universities, the Institute of High Performance Computing A*Star in Singapore, Kyung Hee University in Korea, and Zhejiang University and Dalian University of Technology, both in China. The research, funded by DARPA and the National Science Foundation, appears in Nature (doi: 10.1038/nature12083). For more information, visit: www.illinois.edu