Scientists at Birmingham University (Birmingham, UK) have designed a lens that can be switched to function in either a convex or a concave fashion.
In order to create their dual function lens, the researchers fabricated an array of gold nano-rods on top of flat glass. This enabled them to change the helicity of the light into the glass and hence the positive and negative polarity of the lens.
The lens they developed has an aperture of 80 micrometers - roughly the size of the cross-section of human hair - and a focal length of 60 micrometers.
A recent research paper by Dr. Shuang Zhang, a reader in metamaterials at Birmingham University's school of physics and astronomy described the design of the lens in detail. Published in Nature Communications, it can be found here.
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-- Dave Wilson, Senior Editor, Vision Systems Design