Eye-on-a-Chip Seeks to Mimic Human Vision

Michael D. Wheeler

Scientists are looking to improve on one of nature's wonders -- the human eye. Researchers at the University of Michigan are leading a multiuniversity effort to design a microchip eye that could mimic many of the natural eye's functions but also process non-visible wavelengths. Applications for such a device include target recognition for the military and enhanced surveillance systems.
Led by Pallab Bhattacharya, director of the Solid State Electronics Laboratory at the University of Michigan, researchers are still in the stage of developing a prototype. That prototype likely will consist of an array of micromachined lenses (some measuring only 200 µm wide), tiny vertical cavity diode lasers and tunable light detectors.
The eye will capture incoming light through a variable focus lens array. Tiny prisms positioned behind the lenses will separate the light into bands of red, blue and yellow. A photoreceiver will convert the signals to electric signals and back to optical signals, and vertical cavity surface-emitting lasers (VCSELs) will transfer the information to a microchip or offboard computer for processing. Bhattacharya also is considering a second design, which would skip the prism stage and use tuned photoreceivers and the VCSEL to convert the light into the same three colors.

Human vs. artificial
Although in theory the prototype should simulate the function of a human eye, that may be easier said than done. "If one can image with variable focus and with some amount of variable vision, that's really the objective, and that, by itself, is a lot of work," Bhattacharya said.
Once the team creates an operational prototype that can focus, can adjust to different depths of field and has enough lenses to achieve peripheral vision, the next step will be to incorporate software so the eye can respond to what it sees. "What the eye sees will be fed back to the lenses in a certain fashion so that the lenses can adjust to feedback and high-frequency movements," said Clark Nguyen, an assistant professor of electrical engineering and part of Bhattacharya's team.
Although the scientists still are in the design phase, some already have speculated that the artificial eye could mark an improvement on the human version in several respects. It could be faster than the human optic nerve, and it could use nonvisible wavelengths for night-vision and other applications.