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What to do if the optimizer seems stuck

In certain circumstances the optimizer can not move closer to an optimum in the Levenberg-Marquardt optimization mode. This occurs if aspheric surfaces are present (in which case the ray tracing is iterative), especially when OPD is used in the merit function (which makes the merit function sensitive to small fluctuations in the optical path length).

This problem is fixed by setting the ray acquisition tolerance to a very small value such as 1e-8 mm or even smaller. To change the ray acquisition tolerance, summon the Preferences dialog using Preferences... under the LensForge menu, then go to the Ray tracing tab and enter a new value for the Acquire tolerance.