To use the table glass, enter the file name, including the extension, into the glass column of the Lens Data Editor (or the Material column in Non-Sequential Component Editor) for the desired surface (object).



ZEMAX will internally recognize the dispersion data in the appropriate table glass file in order to calculate the proper index of refraction at each design wavelength.  When computing the data for a specific wavelength, ZEMAX uses a cubic spline interpolation if the wavelength is between the shortest and longest wavelengths defined in the ZTG file. 

To confirm the accuracy of the spline fit, it is important to check the data via the Dispersion Diagram in ZEMAX (Analysis > Glass and Gradient Index > Dispersion Diagram).

From the settings of the Dispersion Diagram, select the desired table glass, and enter the minimum and maximum wavelength range to be plotted.  For the current example, the following settings may be used:



Note the cubic-spline fit between the ten dispersion data points used to define the TABLETEST_2 table glass.  The defined wavelength region in the current example was 3-4 micrometers.  Beyond these wavelengths, ZEMAX uses the index of refraction and transmission data of the nearest data point; no extrapolation of the data is performed.  Therefore, for wavelengths beyond the range of the defined table glass, no fitting is performed, as can be seen by the flat regions at the extent of the wavelength region in the plot below: