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This is called a 'Fresnel lens' or 'zone plate lens', and it focuses light using diffraction rather than refraction.

Using a zone plate instead of a mirror gets around this.

Fresnel telescopes have not been developed in the past because the image formed by one that was large enough to rival a useful-sized reflecting telescope would be several kilometres from the zone plate.

Extrapolating from these results, they think that an orbiting zone plate measuring somewhere between 15 metres and 40 metres across will be enough to distinguish the spectrum of an Earthlike planet at a distance of 30 light-years.

The rings are known as a zone plate.