This article is an update to an earlier article posted by Dan Hill. Fitting of index data in ZEMAX will be demonstrated in this article using the Glass Fitting Tool, located under Tools > Catalogs > Glass Fitting. The “Introduction” and “Defining Transmission Data” sections are nearly identical in this article as in the original article written by Dan, and much of the material from Dan’s original article remains in this article as well.

Introduction – Dispersion Coefficients

ZEMAX includes catalog information for hundreds of glasses from more than a dozen vendors (such as Schott, Corning, Ohara, and Chengdu) around the world. In addition to these vendor specific catalogs, ZEMAX includes data which has been compiled from published sources, such as Laikin’s Lens Design.

Calcite, for example, is one of the many materials in ZEMAX by which the data was obtained by a published source (Handbook of Optics Vol. II). The sources of each material in these catalogs (INFRARED, BIREFRINGENT, and MISC) are documented in the chapter of the ZEMAX User’s Guide entitled "Using Glass Catalogs".

Given that there are hundreds of glasses from various vendors and documented sources, it is often the case that the materials you are designing with are included in ZEMAX’s Glass Catalog database. These glasses are “built-in” to ZEMAX. If the materials you wish to use are not included in ZEMAX, you can take various approaches to modeling them in ZEMAX.

Most commonly, data regarding a specific glass is provided in the form of coefficients corresponding to a specific glass dispersion formula. Some examples of commonly recognized formulas are the Schott formula, the Sellmeier formulas 1-5, the Herzberger formula, and the Conrady formula. ZEMAX supports 11 different dispersion formulas, from which the coefficients for the selected formula can be entered into ZEMAX to properly model the dispersion.

Let’s focus our attention on the Glass Catalog in ZEMAX, which may be opened by clicking on the “Gla” button on the button bar, or by selecting Tools > Catalogs > Glass Catalog from the main menu. Note that as different dispersion formulas are selected from the "Formula" pull-down menu, the coefficients which appear in the Glass Catalog dialog box change accordingly:



Sometimes, the dispersion data available for the glass you wish to model is not provided in terms of coefficients from a dispersion formula. Instead, you may only have a particular set of wavelength-index pairs made available to you by a vendor or other source. That’s okay. You can still use the tools within ZEMAX to “fit” the data for you.