This paper details the motivation for selecting alternate optical materials within an established design and offers considerations when doing so.

1. EXCHANGING OPTICAL MATERIALS

Selecting the material from which a lens is to be made is a fundamental design consideration¹. A chosen material represents the optimum balance of optical and physical attributes going far beyond index and dispersion. Thermal and mechanical effects and index over the wavelength range used must be considered.

Considering all of the factors that influence material selection, the fabricator strives to honor the designer’s selection. Occasionally situations may arise preventing the selected material from being used. The material may no longer be produced, or the material may be unavailable within the allocated manufacturing time. When these cases arise, an alternate material will need to be identified. The material may be an equivalent (within acceptable performance tolerance) or a substitute (outside tolerance for one or more attributes) material. Equivalents are able to be incorporated while keeping desired optical performance, and substitutes would likely require adjustment within the design...

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