Such patterned sheets, called Fresnel zone plates, have long been used for focusing laser beams, but have so far not been used for astronomy.
[1] The long focal lengths of the Fresnel imager (a few kilometers)[2][3] require operation by two-vessel formation flying in space at the L2 Sun-Earth Lagrangian point.
[1] In this two-spacecraft formation-flying instrument, one spacecraft holds the focussing element: the Fresnel interferometric array; the other spacecraft holds the field optics, focal instrumentation, and detectors.
[4][6] In 2008 Laurent Koechlin of the Observatoire Midi-Pyrénées in Toulouse, France, and his team planned to construct a small ground-based Fresnel imager telescope by attaching a 20-centimetre patterned sheet to a telescope mount.
It uses a piece of copper foil 20 cm square with 696 concentric rings as the zone plate.