Good-Bye to Curved Lens: New Lens Is Flat

It could one day be printed on flexible plastic for thin, bendable gadgets

The gently curved lentil served as the namesake for the similarly shaped lens. Future cameras, however, may focus light by relying on flat lenses. Physicists are making major advancements with planar lenses that can scatter and bend rays of light, sans bulge.

As we dream of smartphones that could roll up or slip into a wallet, laboratory researchers have made inroads with flexible circuits, batteries and displays. The millimeters-thick camera lens, however, stands in the way, especially in cases where corrective lenses are necessary to overcome imperfections that would otherwise yield blurry images.

A leap ahead came in 2012, when physicist and engineer Federico Capasso and his colleagues at Harvard University introduced a rudimentary flat, ultrathin lens. Despite its lack of curvature, the glass sliver could focus light via microscopic silicon ridges densely and precisely arranged to bend incoming waves in specific, calculated directions (above). But the lens worked on wavelengths of only one color—and not precisely at that.

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The latest rendition, detailed online in February in the journal Science, has moved beyond proof of concept: it perfectly focuses red, green and blue light, which can be combined to yield multicolor images. The team has since crafted a larger prototype, and it “works exactly like the prediction,” Capasso says. Such lenses could reduce the bulk and cost of photography, microscopy and astronomy equipment. And they could one day be printed on flexible plastic for thin, bendable gadgets. The scientists are in talks with Google and other technology companies. Such low-profile lenses would be useful for new kinds of compact, lightweight displays and imaging systems, says Bernard Kress, principal optical architect at Google[x].

The question is, If it doesn't look like a lentil, can it still be called a lens?