Electronic Design

Liquid Lenses Focus Without Moving Parts

While cell-phone cameras are growing in popularity, their electromechanical autofocus lens systems can be costly and complicated. Yet a liquid lens from Varioptic promises to lower these costs and complexities. Lacking any moving parts, this single-element lens is based on immiscible liquids. Small-diameter lens applications like cell-phone cameras will benefit from this simplicity.

Conventional focus technologies are based on the principle of moving lenses, i.e., precisely shifting delicate glass or plastic elements. The Varioptic approach uses two clear, immiscible liquids that have the same density. One liquid is conductive, while the other is not. The two liquids are sandwiched between panes of glass or plastic, depending on the application (see the figure).

The lens changes its focus through the physics of electrowetting. A current is applied to the conductive liquid, causing it to distend or flatten. This changes the shape of the border between the two liquids, focusing the lens.

Such a single-element lens system has a production cost that's considerably lower than the cost of comparable conventional autofocus lens systems. The lens can focus faster than electromechanical systems, and it consumes about one-tenth their power. Additionally, it requires just half the volume of a mechanical system.

A pair of liquid lenses and a conventional lens to correct for aberrations can form a combination autofocus and zoom lens with no moving parts. The company expects to release this lens for evaluation this year, and production is scheduled for 2006.


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