The polynomial cache can save tremendous time by fitting the criteria change with a polynomial expression.  For a system which has already been optimized, and for moderate tolerances, the criteria as a function of perturbation from nominal is very near quadratic, much like the decenter example we first discussed in this article. 

If your tolerances are too loose, or if the nominal lens configuration is not optimal, then the criteria may have a very strange, un-fittable relationship.  If this happens to be the case, then the fitted polynomial will not be an accurate representation of the true criteria value.  So, don’t set the initial tolerances to be too loose, especially when performing Inverse Sensitivity.

Q:  Are the compensators still considered when using the cache?

Yes, the data which is presented at the end of the tolerance calculation does consider the affects of compensation.  However, compensator data is not displayed.

Q:  How to I clear the cache?

If you every doubt the validity of the cached data, set the “Cache” option to “Recompute All” and repeat the tolerance analysis.