Well, Fresnel Lens is a new word to me. I did not realise that we may be using it without knowing. For example, it is used in Overhead Projectors and lighthouses. Google employees are happily making experiments from this lens. From melting coins, aluminium cans and etc. Quite cool!
BTW, here is a graphical presentation of a Fresnel lens as compared to a normal lens.
Here is how the coins look like after beaming by the lens.
Read all about it at Google Blog
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