This Liquid Lens Changes Its Focal Length As You Apply a Variable Voltage
Researchers from the Hefei University of Technology have developed a variable-focus lens with a difference: It's built around electrically-responsive fluid known as dibutyl adipate (DBA).
"The human eye can arbitrarily focus on objects at different distances at incredibly fast speeds," explains research lead Miao Xu of his team's work. "Inspired by this functionality, we developed an eye-like adaptive liquid lens that can be used to diverge or converge light by changing the shape of the DBA liquid."
The lens, lighter and smaller than its competitors, is created by filling an electrode coated with a water-repellent material with the DBA — which automatically forms into a dome shape. By applying an electrical current, the curvature of the dome can be modified — allowing the lens to change its focal length; switching the voltage off returns the lens to its original state.
The searchers claim that the approach has a number of advantages over current lenses based on adaptive liquids, which typically use an electrowetting approach — making the resulting lenses more complex and more susceptible to failure.
"This type of adaptive liquid lens could one day replace conventional solid lens systems," Xu claims. "This would enable a mobile phone camera that can rapidly change focal length while still being as thin as the phone itself."
There's still work to be done, however: While the prototype lens showed stability from room temperature upwards, the ability to change from 7.5mm to 13.1mm focal lengths, and a 95 percent optical transmittance with a resolution approaching 29 lines per millimeter, the current incarnation requires up to 100V to operate and is considerably slower than motorized equivalents — and building bigger lenses causes issues as gravity begins to effect the dome's shape more than the applied voltage.
The team's work has been published under closed-access terms in the journal Optics Letters.