Millimeter-size spheres of water driven back and forth like a harmonic oscillator can effectively capture high-quality video and images with much faster focusing than conventional methods--without moving any solid parts--say researchers at Rensselaer Polytechnic Institute (Troy, NY). In conventional autofocus cameras, the mechanical focusing mechanism delays the recording of the image, sometimes considerably, from the time the shutter button is pressed. Amir Hirsa, professor of engineering at Rensselaer, and Carlos Lopez, previously a graduate student at Rensselaer and now at Intel Platform Technologies (Jalisco, Mexico), developed a solution to that delay with an oscillating liquid lens that changes the mechanical focusing function into an electrical one, which can therefore capture images much more quickly than conventional shutters. Such adaptive liquid lenses are of interest for high-performance consumer products for their light weight, low cost, and low power requirements. Hirsa and Lopez stumbled upon the idea a few years ago while studying capillary instability and its use in energy-efficient actuation. While working on a capillary switch in an overfilled hole in a hydrophobic plate, Hirsa noticed "what a wonderful lens they produce" (see figure). "Driving these pinned-contact liquid lenses sinusoidally was a natural extension of that work," he says. "We realized that a fast-enough oscillation sets up a resonant frequency so that the lens is nearly always in focus at any given time. Because it takes very little energy to sustain their motion, we wanted to create a lens that focuses nearly instantaneously," says Hirsa.
展开▼
