Army grant for artificial eye

08/01/1998

Army grant for artificial eye

The University of Michigan College of Engineering has been awarded a $1.6 million US Army grant to design an artificial eye on a microchip - an optoelectronic device capable of sensing and processing light. Led by Professor Pallab Bhattacharya, director of the U-M Solid State Electronics Laboratory, researchers hope to combine lenses, tiny lasers, and tunable light detectors to build the chip.

For the Army, this chip could help with extremely accurate remote visual sensing. Possible civilian applications include use in navigation systems for vehicles, robotics, and eventually, to assist people with visual impairment.

Bhattacharya`s team will take two approaches to building a prototype system. Both will capture light with a variable focus lens array and shuttle it to a computer to process the data. The difference between the two versions will be in what happens in between:

 To preserve color, the lens system could be followed by a set of microprisms to separate incoming light into red, blue, and yellow bands. These beams would pass into an array of photoreceivers that generate electrical signals that, in turn, generate light beams at the individual wavelengths through a so-called vertical cavity surface emitting laser (VCSEL).

 The device could skip the prism step and simply use specially tuned photoreceivers with a VCSEL that creates the three desired colors.

Curiously, Bhattacharya believes that the artificial eye will improve on the human version in at least two key respects. Whereas nature`s design converts light into electronic nerve impulses then relays those signals to the brain, the U-M proposal relies on lasers to do the bulk of the transmitting. Because light travels far faster than biological conduction, signals will move more quickly through the manmade device than through an optic nerve. "The scheme will also allow processing of data away from the focal plane, which has several advantages," he said, "including fewer problems with overheated circuits and remote capability."

Yet another advantage of the proposed system is that whereas humans can see light only in the visible portion of the spectrum, the optoelectronic sensor will be able to convert any wavelength of light into usable information. For practical purposes, this means that the device could be used for night vision and ultraviolet detection just as well as for full daylight viewing.

"The human eye is an engineering marvel, and no one has ever been able to duplicate it," Bhattacharya said. "But these optoelectronic devices will eventually be able to simulate the most vital functions."

While Michigan engineers have already done much of the electronics groundwork for the project, there are still several technical problems to solve. These include making variable focal length lenses that, like the eye, can adjust to every depth of field. In addition, the device needs a sufficiently wide array of lenses, as well as the proper processing instructions, to achieve peripheral vision. The detectors will also have to be able to see everything from deep shadows to bright sunlight, and sometimes both at once. Not trivial, the whole system will have to be mounted so it is not sensitive to movement, either by using minute gyroscopes or similar technology.

The U-M engineering group includes Profs. George Haddad, Clark Nguyen, and Sang Lee, and is collaborating with Prof. Dennis Deppe at the University of Texas at Austin. - P.B.