Liquid lenses for camera phones

Clever stuff from France

Camera phones will soon have lenses made from nothing more substantial that a couple of drops of oil and water, but will still be capable of auto focusing, and even zooming in on subjects. So says Etienne Paillard, CEO of French start-up Varioptic.

The company was founded two years ago to exploit two core technology patents covering lenses based on the principles of electro-wetting. This is the tendency of liquid to spread on a substrate, Paillard explains. "It means we can tune the shape of the drop to create a lens. Think about a tunable lens, like in the human eye," he suggests.

The lens has a simple structure: two liquids, of equal density, sandwiched between two windows in a conical vessel. One liquid is water, which is conductive. The other, oil, acts as a lid, allowing the engineers to work with a fixed volume of water, and provides a measure of stability for the optical axis. The interface between the oil and water will change shape depending on the voltage applied across the conical structure. At zero volts, the surface is flat, but at 40 volts, the surface of the oil is highly convex, Paillard said.

The Varioptic lens

There are several obvious advantages to having a lens built like this. Because there are no moving parts, there is less to break and it should be more rugged. Power consumption is also very low: around a tenth of that of a motorised auto focus lens.

It also has the potential to be made very small. Paillard says that at the moment, the limit is a couple of millimetres, but that the company is researching ways of shrinking the lens further. Varioptics is now developing the lens for use in endoscopy as well as in camera phones. But the camera phone market is its priority right now.

The company has a non-exclusive licensing deal with a subsidiary of Samsung to develop the lenses for use in its camera phones. Paillard expects products will be on the shelves by Q1 2006 at the latest, and maybe even in time for Christmas next year.

The first product will be the auto focussing lens, but in another year's time Varioptics will have a true zoom capability, using two of the liquid lenses, Paillard says. "We've just proven in simulation that a 3x zoom is possible. We're building the prototype now."

Varioptics has just filed a further two patents, and will pursue an aggressive intellectual property strategy. "We think, and out patent advisors think, that this is the only way you can do it [build an auto focussing lens] with liquid," Paillard says. "So anyone who wants to build something like this will need a licence from us." ®

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