The Collaborative International Dictionary of English v.0.48:

Illuminator \Il*lu"mi*na`tor\, n. [L., an enlightener, LL. also,
   an illuminator of books.]
   1. One whose occupation is to adorn books, especially
      manuscripts, with miniatures, borders, etc. See
      Illuminate, v. t., 3.
      [1913 Webster]

   2. A condenser or reflector of light in optical apparatus;
      also, an illuminant.
      [1913 Webster]