Insect Eyes Inspire 3-D Lens

May 3, 2006— A three-dimensional optical system based on the eyes of honeybees, houseflies, and dragonflies could allow cameras to see in 360.

The artificial compound eye, reported in the current issue of Science by Luke Lee and his team at the University of California, Berkeley, could be on the market within a few years in ultra-thin camera phones or in small, surveillance camcorders.

"You can capture an image from 0° to 180°. If you have two artificial compound eyes ... you can have a 360° field of view," said Lee.

An insect's domed eye is covered in thousands of tiny lenses that capture light from different angles. Each lens caps a vertical channel that funnels the light to photoreceptor cells, which transmit the light signal to the creature's optic nerve.

Humans have just one lens.

In the past, researchers have tried to replicate the insect system using expensive conventional techniques typically used to manufacture semiconductor chips.

But those methods so far have only produced two-dimensional compound eyes that don't give the highly desired wide field of view.

Ideas from Nature
Lee and his team borrowed from nature to produce a 3-D domed eye that has thousands of light-guiding channels almost identical to those found in insects.

For starters, they designed a template in a piece of photo-sensitive polymer, laying out 8,700 tiny microlenses in a hexagonal honeycomb pattern. On top of those they placed a thin layer of an elastic polymer.

The researchers then attached the flexible layers over the opening of a vacuum chamber and applied a negative air pressure. The pressure pulled the membrane into a bowl shape and also caused the surface to dimple at each of the 8,700 tiny mounds.

The scientists used the bowl as a mold, filling it with a clear resin and exposing it to ultraviolet light to solidify the material.

When Lee popped the hardened resin out of the mold, he had a transparent dome a couple of millimeters in diameter and covered with 8,700 tiny mounds.

Next, the researchers used a component called a condenser lens to shine a spoke-like pattern of ultraviolet light onto the dome so that each spoke of light would hit the dome at a different angle.

Each of the tiny mounds worked like a lens to focus the incoming light into the rest of the light-sensitive material beneath. The light drilled into the material, creating 8,700 vertical channels, all pointing toward the center of the dome.

"One of the strengths of this work is that he has demonstrated that he can do this thing very simply," said Edoardo Charbon, a professor and expert in high-performance imaging at the Swiss Federal Institute of Technology in Lausanne.

A cross-section of Lee's artificial compound eye looks remarkably similar to a cross-section of a natural compound eye.

The idea, said Lee, is to place light-collecting components, such as photodiodes or charge-coupled devices used in digital cameras, at the bottom of the channels to capture the light signal and send it to a processor.

Software would then convert the data coming from multiple lens into a image appropriate for the final device, whether that's a camera or a medical imaging device.

The challenges for Lee, said Charbon, lie in both science and industry.

"If one can find a way to make this model easily standardized and be handled by existing technological processes, then it has a great future," said Charbon.