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Mechanical, Aerospace, and Nuclear Engineering

Liquid Lenses May Lead To Smarter Cameras

New miniature image-capturing technology powered by water, sound, and surface tension could lead to smarter and lighter cameras in everything from cell phones and automobiles to autonomous robots and miniature spy planes.

Rensselaer researchers have designed and tested an adaptive liquid lens that captures 250 pictures per second and requires considerably less energy to operate than competing technologies.

The lens 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.

“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,” says project leader Amir Hirsa, professor and associate department head for graduate studies in the Department of Mechanical, Aerospace, and Nuclear Engineering. “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.”

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Liquid Lenses May Lead To Smarter Cameras
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This series of time-lapse photos shows how the lens, made up of two droplets of water vibrating at a high speed, changes shape and, in turn, moves in and out of focus.
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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. This takes both time and valuable energy. Hirsa said 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.

Hirsa’s new method couples two droplets of water through a cylindrical hole. When exposed to certain frequencies of sound, the water droplets resonate back and forth with great speed and a spring-like force.

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. The images are captured electronically, and software can be used to automatically edit out any unfocused frames, leaving the user with a stream of clear, focused video.

“The great benefit of this new device is that you can create a new optical system from a liquid lens and a small speaker,” Hirsa says. “No one has done this before.”

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Rensselaer (ISSN 0898-1442) is published in Spring, Summer, Fall, and Winter by the Office of Strategic Communications and External Relations, Rensselaer Polytechnic Institute, Troy, NY 12180-3590. Opinions expressed in these pages do not necessarily reflect the views of the editors or the policies of the Institute. ©2008 Rensselaer Polytechnic Institute.