A technique for accurately figuring very thin, lightweight lenses is discussed. The phase change required to focus a plane wave into a point is calculated and photographically plotted with exposure proportional to phase (scaled from 0 to 2π). The plot is photoreduced and the photoreduction is etched, with the depth of etch approximately proportional to the exposure. The result is a kinoform lens. Photographs taken with a kinoform lens are included.
J. A. Jordan, Jr., P. M. Hirsch, L. B. Lesem, and D. L. Van Rooy, "Kinoform Lenses," Appl. Opt. 9, 1883-1887 (1970)