An artificial electronic retina that can "see" in a similar way to the human vision system and can recognize handwritten digits has been built by KAUST researchers as they seek to develop better options for computer vision applications.
Mani Teja Vijjapu, an electrical engineering Ph.D. student, Khaled Nabil Salama and coworkers have designed and fabricated an array of photoreceptors that detect the intensity of visible light via a change in electrical capacitance, mimicking the behavior of the eye’s rod retina cells. When the array was connected to an electronic CMOS-sensing circuit and a spiking neural network (a single-layer network with 100 output neurons), it was able to recognize handwritten numbers with an accuracy of around 70 percent.
“The ultimate goal of our research in this area is to develop efficient neuromorphic vision sensors to build efficient cameras for computer vision applications,” explained Salama. “Existing systems use photodetectors that require power for their operation and thus consume a lot of energy, even on standby. In contrast, our proposed photoreceptors are capacitive devices that don’t consume static power for their operation.”
The photoreceptor array is made by sandwiching a material with suitable optical and dielectric properties between a bottom aluminum electrode and a patterned top electrode of indium tin oxide to form a pixelated array of miniature light-sensitive metal-insulator-metal capacitors. The array is made on a thin substrate of polyimide so that it is flexible and can be curved as desired, including a hemispherical shape mimicking the human eye.
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