Camera lens controls light with sound

 

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Posted on 13 Oct 2008 at 16:18

A technique which allows the creation of liquid lenses powered by water, sound and surface tension could be used to create a new generation of low-cost, lightweight and energy efficient cameras.

The adaptive liquid lenses are being developed by researchers at Rensselaer Polytechnic Institute. The component is made up of a pair of water droplets, which vibrate back and forth upon exposure to a high-frequency sound, and in turn change the focus of the lens.

By using imaging software to automatically capture in-focus frames and discard any out of focus frames, the researchers can create streaming images from lightweight, low-cost, high-fidelity miniature cameras, according to the engineers.

The lenses have been shown to be capable of capturing 250 pictures per second and require "considerably less energy to operate" than competing technologies.

"The lens is easy to manipulate, with very little energy, and it's almost always in focus - no matter how close or far away it is from an object," said project leader Amir Hirsa.

"There is no need for high voltages or other exotic activation mechanisms, which means this new lens may be used and integrated into any number of different applications and devices."
He explained that most current methods for manipulating liquid lenses involve changing the size and shape of the area where the liquid contacts a surface, in order to bring an image into focus.

However, a key feature of his new technique is that the water stays in constant, unchanging contact with the surface, thus requiring less energy to manipulate.

To achieve this, the new method couples two droplets of water through a cylindrical hole. When exposed to certain frequencies of sound, the device exploits inertia and water's natural surface tension. The water droplets resonate back and forth with great speed and a spring-like force. Researchers can control the rate of these oscillations by exposing the droplets to different sound frequencies.

By passing light through these droplets, the device is transformed into a miniature camera lens. As the water droplets move back and forth through the cylinder, the lens moves in and out of focus, depending on how close it is to the object.

Author: Robert Jaques