Computer Generated Holographic Optical Elements as Replacements for Glass Elements in Visual Systems.

Because of their versatility in unusual geometries, very low weight, and potential for exceptionally low production cost, holographic optical elements are receiving increased attention as replacements for conventional optical elements in a variety of applications. They are usually produced in the laboratory with lasers and stabilized optical fixtures that often involve the use of complex and costly glass optics to produce the proper construction beams. The use of computers to generate holographic optical elements is an attractive alternative to the laboratory method in that it offers potential for low production cost as well as the greater versatility afforded by a fully integrated digital design and fabrication capability that eliminates lasers and expensive glass construction optics. However, until recently, the limited resolution of computer plotters did not permit the generation of large aperture holographic optical elements. Thus prior work has been limited to the fabrication of small experimental lenses and mirrors. The primary effort of this dissertation was to overcome resolution limits by exploiting two new methods capable of producing large aperture computer generated holographic lenses: (1) a photoreduction process in which a computer controls a high speed, medium resolution xerographic type plotter to make a master pattern that is then photoreduced on silver halide film; (2) a unique direct write technique that uses a computer controlled electron beam to write the lens pattern directly on silver halide film. Using the first method, thirty identical f/10.7 binary kinoform lenses were produced, thus demonstrating the ease of mass production afforded by the photoreduction process. The second method, with its high resolution, grey shade, and direct write capability, was used to produce a 100 mm diameter, f/10 amplitude hologram lens with 2,000 fringes. Bleached lenses of both types were evaluated in a group of optical tests, and two telescopes were constructed using the two types of lenses as the objective lens. Both telescopes, especially that using the electron beam generated lens, provided telescopic photographs of the moon that clearly demonstrate the potential for computer generated holographic lenses to compete with glass optics in standard optical systems.