All animals have curved imagers for their eyes. By contrast, artificial vision systems such as digital and video cameras have to rely on flat image-recording surfaces. These artificial imagers are made with silicon microfabrica-tion technologies to produce the necessary network of semiconductor photodetectors, and they can now create pictures with more than ten million pixels. But there remains the big problem of producing bright, distortion-free images with a flat imager. Given the distortion that occurs at the edges of lenses, multiple combinations of different lenses are required for effective imaging. Consequently, lens arrangements are heavy, expensive and produce darker results than they would otherwise do.
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