Drawing inspiration from an insect's multi-faceted eye, University of Wisconsin-Madison engineers have created tiny lenses with vast range of vision. An array of the miniature lenses — each no bigger than the head of a pin — can capture a panorama image covering a 170-degree field of view.
The half-millimeter diameter lenses resemble a series of ripples on water emanating out from the splash of a stone. In bull's-eye fashion, each concentric ring alternates between bright and dark. The distance between the rings determines the optical properties of the lens, and the researchers can tune those properties in a single lens by stretching and flexing it. Tiny silicon nano-wire towers make up dark regions of the flexible Fresnel zone lenses.
The flexible Fresnel zone plates focus by diffraction — bending light as it passes the edge of a barrier. The Fresnel components could allow surgical scopes to capture a broader perspective at a fraction of the size required by conventional lenses.
Black silicon, or clusters of microscopic vertical pillars, traps light inside the dark regions of the lenses. Incoming light bouncing between individual silicon nanowires cannot escape the complex structure, making the material even darker and providing crisp focusing capabilities.