Proceedings PaperThe Zone Plate: A New Lease Of Life?
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It has long been known that zone plates can be used to form an image but they have been little used in practice because a lens generally performs better. Since a zone plate distributes light into several diffracted orders the efficiency is low and since the focal length is inversely proportional to wave-length the chromatic aberration is enormous. However, despite these drawbacks the zone plate does possess some attractive features: it is a thin structure so it produces no distortion in the image; it is less bulky and lighter than a lens (which would be particularly important for many infrared applications), and can be replicated so it is amenable to inexpensive mass production. We suggest that there are 3 main reasons why zone plates might become more widely used: a change of requirements; improvements in manufacturing technology; and new applications which take advantage of the unique features of the zone plates.