The Criterion tab is used to define the figure-of-merit used for the tolerancing. This is usually related to, but not the same as, the Optimization merit function.

The  Tolerancing Criterion is usually purely optical (whereas the Optimization merit Function may contain many boundary conditions that must be satisfed). For convenience, ZEMAX offers some of the most common tolerancing criteria as selections from a drop-down list, including parameters like:

spot radius
wavefront error
MTF
boresight error
angular radius

Whatever you choose is ultimately expressed as a merit function, and you can choose to create your own tolerancing criterion in the merit function and use that if you wish.

For the purposes of this article, configure this tab as follows:



We want the manufactured system to have RMS wavefront error better than l/20, or 0.05 waves. Therefore, we will use RMS wavefront error as the tolerancing criterion, and we will optimize the interlens separation using the DLS optimizer. We will perform just three cycles of optimization, because on the shopfloor the separation will not be adjusted exhaustively: three cycles of optimization is plenty.