A space-based telescope that uses a thin plastic membrane as a lens is being developed by the United States Air Force.
Called a photon sieve, it works by bending light through billions of tiny holes in the "cling film" style optic.
Unlike in existing traditional mirror-based telescopes, the new lens can be folded to fit into a tiny space.
More: http://www.bbc.co.uk/news/science-environment-19758442 (http://www.bbc.co.uk/news/science-environment-19758442)
A more technical document for FalconSAT-7 be found here:
http://www.amostech.com/TechnicalPapers/2011/Optical_Systems/ANDERSEN.pdf
Points to note:
1) Each wavelength comes to focus at a different distance behind the clingfilm
2) So the camera is placed at the focal point of the wavelength of interest (H-alpha for this solar scope)
3) I'm guessing the camera has a H-alpha filter to reject all other (out of focus) wavelenths
It's a clever idea! When will Lunt/Coronado start selling them?
Mark