A model has been developed which predicts the chromatic properties of gradient-index materials based on the composition of the glass. It yields a gradient Abbe number and a gradient partial dispersion which can be used by the lens designer in the design of achromatic gradient-index lens systems. Over 100 glasses with various ion exchange pairs have been investigated. The result is a gradient Abbe number ranging from −2000 to +5000 and a gradient partial dispersion ranging from −5 to +7. This wide range of gradient Abbe numbers and gradient partial dispersions can be further extended by using a glass which has two exchange ions with one diffusing ion or a glass which has one exchange ion with two diffusing ions. In addition to an extended range, the designer is afforded the luxury of a continuously varying Abbe number rather than the discrete Abbe number of conventional materials.
© 1985 Optical Society of America
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