February 9, 2006 - Last week, French optics company Varioptic announced the availability of their new Arctic 320 lens, a multi-megapixel liquid lens capable of extremely swift autofocusing, designed for camera phones. Varioptic calls such a lens "the industry’s first" and there is no reason to dispute this claim. Liquid lenses (and mirrors) are an old concept, but only recently has the technology caught up with the theory. However, though Varioptic is at the head of liquid lens development, other organizations are still trying different approaches to the idea.
The lenses by Varioptic, including the Arctic 320, are constructed out of two different drops of liquid. One of these drops can conduct electricity; one cannot. These drops are nestled one on top of another in a conic-shaped ring of metal, and above and below them are thin panes of a solid translucent material to keep the drops in place. When a minute electrical charge is applied to the metal, the conductive fluid reacts and changes shape—a process called ‘electrowetting’—and the light passing through the panes bends in accordance with the shape of the curve between the two liquids.
After Samsung Electro-Mechanics Co (SEMCO) licensed the technology for development, Varioptic lenses made their debut at CeBIT in March 2004—and so did FluidFocus lenses, a nearly identical liquid lens prototype by Philips Electronics. Philips’ version uses a straight cylindrical metal ring enclosing the droplets instead of a conic-shaped ring, which Varioptic didn’t think was enough of a difference.
On March 17 of 2004, two weeks after Philips announced intentions to demonstrate its lens at CeBIT, Varioptic issued a press release stating that they were going to take legal action. Varioptic claimed that Philips was infringing upon patents that the French company had received in 1997 and 1999 in Asia, Europe, and the US by intending to profit from the technology without licensing it. The exact outcome of this confrontation is unknown, but Philips has been very quiet about its FluidFocus lenses for quite some time.
While Varioptic and Philips were demonstrating their prototypes at CeBIT, US-based Lucent Technologies’ Bell Laboratories was working on a liquid lens of its own. Bell Labs’ version involved a drop of conductive liquid on a metal plate as well, but this plate contained many electrodes that could ‘fine-tune’ the movement of the drop with each electrode activated.
At the close of that year in December of 2004, De-Ying Zhang, Nicole Justis, and Yu-Hwa Lo from the University of California at San Diego published a piece in Optics Letters that outlined their own version of a liquid lens. This type is composed of two drops of fluid, each sealed within a membrane and placed on both sides of a thin piece of glass. The two drops are connected to tiny valves which can increase and decrease the internal pressure, thus changing the curvature of the membrane and therefore the focal length. Since this process does not use electrowetting, but rather uses simple pressure to mimic the way human eyes focus, it is markedly different from Varioptic’s approach and could probably be developed and distributed without legal interference.
Finally, Singapore-based PGS Precision Pte Ltd licensed technology from the Institute of Materials Research and Engineering (IMRE) in July of 2005 that used a similar approach. Called fluidlens, this liquid lens system also uses pressure from valves rather than electrowetting to change the shape of a fluid’s surface to focus light passing through, and the IMRE zoom lenses also involve two drops of liquid on either side of a glass plate. (We reported on the full story here: http://www.digitalcamerainfo.com/content/Scientists-in-Singapore-Create-Liquid-Lens-that-Zooms-Without-Electricity-.htm). However, despite such a similar construction in lens design to the lens developed by the University of California at San Diego, no apparent legal conflict has yet resulted.
Aside from the lure of the unconventional concept, liquid lenses are so appealing because they have no moving parts and are therefore extremely quiet. They are also inexpensive to manufacture, extremely durable, able to function in a wide range of temperatures, and very difficult to wear out. So far, size is the main hurdle left; the Arctic 320 reflects Varioptic’s commitment to developing lenses for camera phones, and while the Varioptic website lists many of the other applications of the technology—everything from endoscopy to web cams—developing larger lenses may be difficult. Surface tension and electromagnetism may be enough to aid the shape of very small liquid drops, but the surface to volume ratio of larger lenses is a law of physics that’s much harder to get around.
Still, lenses suitable to dedicated digital still cameras are probably not far off, especially since Varioptics is already fighting for a niche in the camera phone market. If you’re a casual point-and-shooter, be on the lookout during the next two or three years for ultra slim compacts sporting a liquid lens—but if you’re a pro, don’t plan on selling your Sigma collection just yet.