Engineers often turn to nature for inspiration for their newest innovations. When it comes to adaptations, nothing can beat millions of years of evolution. That's why, when Madison-based engineers were looking to develop new, minuscule lenses with incredible visual fields, they turned to those who were there first: insects.
Insects have compound eyes, which essentially means they have hundreds or even thousands of small "eyes" that function independently, but communicate with each other to give the insect an incredible field of view. Consider this: The field of view in a single human eye is around 100 lateral degrees. That is, if you close one eye, and focus straight ahead of you, you will see a little more than 90 degrees worth of space, including the area of focus and the periphery to the side of you. Open both eyes, and that visual field almost doubles, but with some overlap in the middle. That's why we can see what's ahead of us much more clearly than what's on the sides.
Now, get this: Bees can see more than 300 degrees, almost all the way around their heads. Impressive, no doubt, but trust me: you don't want to see this way if you want to keep appreciating fine art. The effect is a pixelated mess of shapes. Still, it's a much more effective way to collect tons of visual information. And when you're fighting to survive in a world that wants to swat you dead, good eyesight is paramount—even more than an appreciation for beauty.
The University of Wisconsin-Madison's engineering team are exploiting this very capability to make tiny lenses with the same kind of precision and field of vision, and they've added some improvements. According to a press release, the new lenses have a 170-degree field of view, in one single lens. Remember, one of your eyes only gives you 100 degrees.
Conventional lenses, including eyeglasses, use refraction to focus, but the new lenses use a completely different process: diffraction. In diffraction, light changes as it hits the edge of a surface. And with the new lenses, there are several "levels" to the lens, allowing light to hit "edges" throughout. The same has been attempted in the past, but never with the accuracy seen here; there was always some fuzziness in the resultant product. The Madison team was able to overcome this hurdle using new materials.
The new lenses are less than a half-millimeter across. If you have an average screen and aspect ratio, that's likely about the size of the period at the end of this sentence. The engineers hope they can be used as surgical tools, and in security cameras.
A report on this work can be found in the Oct. 30 issue of the journal Scientific Reports.
Photo: USGS Bee Inventory and Monitoring Lab | Flickr