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The First Analog Silicon Retina


With his student Misha Mahowald, computer scientist Carver Mead at Caltech described the first analog silicon retina in "A Silicon Model of Early Visual Processing," Neural Networks 1 (1988) 91−97. The silicon retina used analog electrical circuits to mimic the biological functions of rod cellscone cells, and other non-photoreceptive cells in the retina of the eye. It was the first example of using continuously-operating floating gate (FG) programming/erasing techniques— in this case UV light— as the backbone of an adaptive circuit technology. The invention was not only potentially useful as a device for restoring sight to the blind, but it was also one of the most eclectic feats of electrical and biological engineering of the time.

"The approach to silicon models of certain neural computations expressed in this chip, and its successors, foreshadowed a totally new class of physically based computations inspired by the neural paradigm. More recent results demonstrated that a wide range of visual and auditory computations of enormous complexity can be carried out in minimal area and with minute energy dissipation compared with digital implementations" (, accessed 12-23-2013).

In 1992 Mahowald received her Ph.D. under Mead at Caltech with her thesis, VLSI Analogs of Neuronal Visual Processing: A Synthesis of Form and Function. 

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