zone-platehttp://www.oed.com/dictionary/zone-plate_n%3Ftab%3Dmeaning_and_usezone plate, n.
First published 1921; not fully revised

zone platenoun

  1. 1890–
    A plate of glass marked out into concentric zones or rings alternately transparent and opaque, used like a lens to bring light to a focus.
    1. 1890
      A zone plate has therefore the power of a condensing lens.
      T. Preston, Theory of Light ix. 178
    2. 1937
      The intensity of the image produced with a zone plate will be greater if alternate zones are not blocked out but are left transmitting, with a phase difference of one half period introduced between them and adjacent zones.
      G. S. Monk, Light xii. 167
    3. 1978
      When the zone plate is illuminated with an X-ray plane wave, a converging spherical wave will come out.
      Scientific American November 65/1

Originally published as part of the entry for zone, n.

zone, n. was first published in 1921; not fully revised.