There have been significant advances in optics recently.  Scientists created the first robotic eyeballs that may one day give vision to the blind and eyes to battle robots.  Scientists also delved into the world of micro-optics, creating tiny microscopes that could one day be incorporated into a system on a chip.  Now scientists have come up with perhaps their most exciting optical breakthrough yet -- controlling light with sound. 

The new tech, developed by Rensselaer Polytechnic Institute, uses far less power while offering superior fidelity to traditional lenses.  It uses a special pair of liquid lenses called adaptive liquid lenses.  Vibration from high frequency sound causes the droplet lenses to bulge and contract, focusing the camera.

As pictures are taken at a rate of 250 frames per second, computer software determines "in focus" frames and drops out of focus ones.  The ingenious setup is highly advantageous in that it’s highly accurate, low-cost, and extremely lightweight.

Project leader Amir H. Hirsa, professor and associate department head for graduate studies in the Department of Mechanical, Aerospace and Nuclear Engineering at Rensselaer states, "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.  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."

The paper about the research, entitled "Fast focusing using a pinned-contact oscillating liquid lens" will appear in the journal Photonics in October, and is currently available online.

Most current methods for manipulating the small liquid lenses found in cell phone cameras and other devices rely on physically manipulating the surface area that the droplet rests on.  This takes much more time and energy, whereas the new method is fast and low-power.  The savings result from not having to engage in the energetically costly method of manipulating surface contact.

On a most basic level, the new device consists of the two droplet lenses and a cylindrical tube connecting them.  When exposed to sound, the droplets and the air in the tube oscillates, creating a pendulum effect of sorts.  This oscillation focuses the camera, at a certain stage in the oscillation.  It can be controlled by changing the frequency of the sound, allowing for potential focusing improvements in the camera.

The end result is a stream of clear, focused video.  Professor Hirsa states, "The great benefit of this new device is that you can create a new optical system from a liquid lens and a small speaker.  No one has done this before."

However, the full potential of the device is only just beginning to be exploited.  The new device's oscillation is also controlled by the size of the droplets.  By using a small aperture and properly selected droplets, Professor Hirsa believes a frame rate of 100,000 pictures per second should be possible, with sufficient light for each picture.

Aside from cell phones, the tech could see its way into systems on a chip and unmanned aerial vehicle cameras.  By lending eyes to the next generation of UAVs the device could boost homeland security.

Professor Hirsa worked with Carlos A. Lopez, who earned his doctorate at Rensselaer and now works for Intel Corp.’s research and development lab in Mexico on the project.  The pair has also applied for a patent for technology.

The research was funded by the U.S. National Science Foundation.