Radio lens could be a view of the future

Prototype contact lenses that can be used as biosensors have been developed by Babak Parviz at the University of Washington, in the US. The prototype can be used to display body chemistry or as a heads up display (HUD).

Powered by radio and 330 mW from a loop antenna that picks up power beamed from nearby radio sources, future versions will also be able to harvest power from a mobile phone.

In his early tests, rabbits safely wore contact lenses with metal connectors for electronic circuits. The prototype lenses contained an electric circuit as well as red LEDs for a display. The lenses were tested on rabbits for up to 20 minutes and the animals showed no adverse effects.

Fitting a contact lense with circuitry and power is complex. The circuitry has to be transparent so as not to annoy the wearer. Also, techniques had to be developed to deal with the temperatures and chemicals used in large-scale microfabrication so that the polymer material used by the contact lenses is not ruined.

”Conventional contact lenses are polymers formed in specific shapes to correct faulty vision,” says Dr Parviz.

“To turn such a lens into a functional system, we integrate control circuits, communication circuits and miniature antennas into the lens using custom-built optoelectronic components.

“Those components will eventually include hundreds of LEDs, which will form images in front of the eye, such as words, charts and photographs. Much of the hardware is semitransparent so that wearers can navigate their surroundings without crashing into them or becoming disoriented.”

The prototype includes a lens with one LED powered by RF.

“What we’ve done so far barely hints at what will soon be possible with this technology,” continues Parviz.

The power for the lens comes through an antenna that collects incoming RF energy from a separate portable transmitter. Power-conversion circuitry provides DC to other parts of the system and sends instructions to the display control circuit.

The display - at the centre of the lens - can consist of multiple LEDs that turn on and off. Their transparency is modulated by the control circuit.

An energy-storage module such as a large capacitor can be connected to a solar cell to provide a power boost to the lens. A biosensor samples the surface of the wearer’s cornea, performs an analysis and then provides data to the telecommunication module to transmit to an external computer.

Such a contact lens will obviously spend hours touching the human eye. Parviz’s team wants to explore the depth and breadth of information that can be captured by wearing the contacts - for example, diabetics can monitor their blood sugar levels.

The lens can sample the information obtained from the eye’s surface and display the results in front of the eye as a HUD.

The first HUDs were used in the military, based on static gun sight technology for military fighter aircraft with a ring and dot of light called the ‘pipper,’ which projected onto the clear glass in front of the sight.

HUDs were soon developed to display computed gunnery solutions - using aircraft data such as airspeed and angle of attack - to greatly increase the accuracy pilots could achieve in air-to-air battles.

University of Washington

www.washington.edu