In practice, few optical systems other than eyeglasses rely on single lenses.
Usually, different lenses with different properties are stacked on top of each other to remove aberrations
and achieve full-colour wide-angle images. Dr Yu's lenses can be stacked in this way, too.
并实现全色广角图像 。虞博士的透镜也可以这样叠加 。
By sandwiching three of them together, he has created a triplet that achieves almost all the control of light waves
that would be expected of bigger and heavier glass-lens systems.
Besides saving weight and volume, Dr Yu's flat lenses also promise to be cheaper to mass produce than the conventional sort.
Grinding and polishing a glass lens is complex and time-consuming.
Flat lenses are made using nanolithographic techniques, which are also employed for making computer chips.
Given these advantages, flat lenses could replace their bulkier counterparts anywhere that cost or weight is an issue
—meaning pretty-well everywhere from microscopes and cameras, to pairs of spectacles.
Flat lenses still need development before they can truly replace their glass counterparts.
In current designs, only around half of the light falling on a flat lens triplet makes it through to the other side.
The rest is reflected or absorbed by the material. In a typical glass lens, by contrast, at least 90% of the light passes through.
剩余的都被材料反射或吸收了 。相反，在一个传统玻璃镜片中，至少90%的光线都能穿过去 。
However, the researchers hope that, by tweaking the shapes and positions of the antennae, they will be able to improve on this.
In theory, there is no limit to the size of a lens that could be made using Dr Yu's techniques.
But there are practical challenges in making ever-larger lenses that would work well in full colour.
In particular, the bigger the lens, the more challenging it becomes to design the correct shape and distribution of antennae.
These technical obstacles will no doubt be overcome—and probably quite quickly,
given the interest the project has attracted from America's armed forces.
Meanwhile, flat lenses for smaller applications are already on course
to become the biggest innovation for manipulating rays of light since someone, thousands of years ago,
first ground a piece of transparent crystal into the shape of a leguminous seed.
...a respectable married woman with conventional opinions.
It's just very time consuming to get such a large quantity of data...
The Foreign Minister held talks with his Chinese counterpart.
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