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Liquid lens can magnify at the flick of a switch

作者:褚惧沱    发布时间:2019-03-01 06:04:06    

By Tom Simonite The first liquid camera lens with no moving parts, and that can switch between two levels of magnification, has been designed by a German research team. The work is an important step towards liquid zoom lenses that can sweep through a range of magnifications. Liquid lenses bend light using the curved boundary between watery and oily liquids. When the two liquids are held in the right container, the boundary between them can be made to curve in a way that focuses light simply by applying a voltage. Liquid lenses have attracted much attention because they are potentially smaller than conventional optics and cheaper to build. Samsung has already built them into some cellphones. But the greatest savings in size and cost can be made with zoom lenses. Altering the focusing power of a set of liquid lenses should provide the same effect as changing the distance between solid, fixed-focus lenses in a traditional zoom lens. “That would remove the need for mechanical parts, which would be a major advantage,” says Peter Schreiber, a researcher at the Fraunhofer Institute for Applied Optics and Precision Engineering, Jena, Germany. Small, robust, liquid-based lenses could be integrated more easily into cellphones and other portable gadgets. But changing a zoom lens’s magnification also affects its focus, and causes problems such as pincushion distortion and chromatic aberration. Conventional zooms often require 20 or more lenses – many that move – to preserve image quality across the whole range of magnification, but nobody has come up with a liquid lens design that can do that. A first step, however, is to design a lens that offers different levels of magnification rather than a continuous range. Schreiber and colleagues Frank Wippermann and Andreas Bräuer worked with French company Varioptic, which has pioneered liquid lenses, to come up with a design that switches from a normal view to 2.5-times magnification. The design consists of four liquid lenses and three fixed plastic lenses. When the four liquid lenses are at their most curved, the optics offer a magnification of 2.5 times. When all four lenses are at their flattest there is no magnification. The complete length of the system from outer lens to image sensor is 29mm, but it should be possible to reduce that, says Schreiber. Varioptic is now considering how to take the design on to the prototype stage. The lenses are arranged to prevent image distortion. But to minimize color distortion, red, green and blue images must be recorded in sequence and then combined digitally. That process would increase exposure times, admits Schreiber,

 

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