Gradient Index Lens Fabrication Processes: A Review

Processes for producing index-of-refraction variations in optical materials (e.g., glasses, plastics, and single crystals) are reviewed in the context of fabricating graded index lenses for optical imaging systems. The following criteria are considered: (a) the underlying scientific principles, (b) size and shape of lenses in which the gradient can be produced, (c) index levels and maximum index differences obtainable, (d) degree of control over gradients produced, (e) wavelength regions in which the transparency can be obtained, and (f) nature of materials: glasses, plastics, or crystals.