這種透鏡的主要優(yōu)點：可以通過電控來變換焦距的遠近的透鏡,。也許在將來的某一天，它會成為傳統(tǒng)雙焦透鏡之外的選擇,。
人眼睛里面的天然透鏡使光線彎曲,，在位于眼睛后部的視網(wǎng)膜上聚焦。如果眼睛有畸形或者不能正常完成這一生理功能,，玻璃體就會幫著讓光線經(jīng)過一個稱為折射的過程---這和一頭淹在水里的棍子看起來彎曲是一個道理,。透鏡的折光度取決于透鏡本身的精細(xì)形狀和曲率。雙焦透鏡的主要原理是兩個透鏡被磨成一塊,，或者玻璃，或者塑料,。 與此相反,這種新的電子透鏡是平面的,。它依照衍射原理聚光。衍射時,，光波的波峰和波谷疊加時相互抵銷,，而波峰和波峰或者波谷和波谷疊加時相互加強。
據(jù)位于圖森的亞利桑那大學(xué)光學(xué)科學(xué)家李國強（音）和Nasser Peyghambarian 以及他們的同事報道,這種新的透鏡里面有一層液晶,，夾在兩層玻璃之間,。玻璃的內(nèi)層有一個電極安裝在環(huán)形的透明電極，固定在一個榫頭模型里面,。施加電壓在這兩些電極中的任何一個都會起到加速的作用,，這樣光就可以通過透鏡的那個部分。 這樣,通過不同的環(huán)的光可以同步出來,。
這聽起來可能是不怎么好,，但是,，通過調(diào)節(jié)環(huán)上面的電壓，使得對光線的削弱和加強作用使得它這樣的平板能夠?qū)膺M行聚集,。所以通過簡單地施加電壓,，他們可以讓這種裝置從一個透明的平板變?yōu)橐粋€透鏡。這就是本周他們在《美國科學(xué)院院報》上的報道,。他們讓這種透鏡適合于老花鏡,，又能夠通過電來實現(xiàn)開關(guān)控制，就像這些研究人員提供的一個原型那樣,。對于雙焦透鏡來說,，這種新的電鏡可以和一個標(biāo)準(zhǔn)透鏡聯(lián)合起來做成一個透鏡，它的聚集能力在電路接通時會得以增強,，李國強說,。
與雙焦鏡頭相比，“它的優(yōu)點是,，你可以獲得整個視野更正的一個全面的區(qū)域”,，哥倫比亞俄亥俄州立大學(xué)的視覺科學(xué)家Mark Bullimore這樣說。這種鏡頭不僅可以和傳統(tǒng)眼鏡競爭,，而且可以和隱形眼鏡競爭,。這種鏡片可以通過外科手術(shù)植入眼睛。而且,，Bullimore還說,，“如果這項技術(shù)成熟了的話，我可以預(yù)見這將對某些病人具有強烈的吸引力,。”
英文原文
'Letric Specs.
Carefully tuned voltages can change the focusing power of these prototype glasses (above) and bring a blurry image into focus.
Credit: PNAS
Bye Bye Bifocals
By Adrian Cho
ScienceNOW Daily News
3 April 2006
Here's the long and short of it: A lens that electronically switches its focus from far to near may someday provide an alternative to traditional bifocal lenses.
The natural lens in your eye is supposed to bend light rays and focus them on the retina at the back of the eye. If the eye is misshapen or not strong enough to do the job itself, glasses help bend the light rays through a process called refraction--the same one that makes a stick appear to kink when one end is submerged in water. Just how much a given lens bends light depends on its precise shape and curvature. Bifocals are essentially two lenses ground into a single piece of glass or plastic. In contrast, the new electronic lens is flat and focuses light through a phenomenon known as diffraction, in which light waves overlap either peak-to-trough to cancel one another out, or peak-to-peak to reinforce one another.
The new lens consists of a layer of material known as a liquid crystal, which is sandwiched between two thin sheets of glass, report optical scientists Guoqiang Li and Nasser Peyghambarian of the University of Arizona in Tucson and colleagues. The inner surfaces of the glass sheets are covered with circular transparent electrodes arranged in a bulls eye pattern. Applying a voltage to one of these electrodes affects the speed with which light can pass through that part of device. So light waves passing through different rings get out of synch with one another.
That may sound like a bad thing, but by adjusting the voltages on the rings, the researchers exploited the canceling and reinforcing effects to make the flat plates focus the light. So simply by applying the voltages, they could switch the device from a transparent plate to a lens, they report online this week in Proceedings of the National Academy of Sciences. That makes the lenses suitable for reading glasses that can switch on and off electronically, as the researchers demonstrated with a prototype. As for bifocals, the new technology could be combined with a standard lens to make one whose focusing power increases when the electricity is switched on, Li says.
Compared to bifocals, "the advantage to this is that you get a full field of view correction," says vision scientist Mark Bullimore of Ohio State University in Columbus. Such electronic lenses would have to compete against not only traditional glasses but also bifocal contact lenses and lenses surgically implanted in the eye. Still, Bullimore says, "if the technology were to mature, I can see where this might be an attractive option for some patients."
