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Tolerance script - saving Monte Carlo tolerance values for use in several optimizations

  • 25 May 2023
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I am trying to use tolerance scripts to realistically model my lab’s compensation procedure. The system consists of several lenses mounted in two lens barrels that fit together. If the performance of the system is not compliant, then one of the barrels is rotated 90º with respect to the other and the performance is checked again; subsequently it can be rotated 180º or 270º as needed. 

I am thinking to model this by using multi-configuration for each of the barrel rotation options (0º, 90º, 180º, 270º), but as the system is nominally rotationally symmetric, this by itself will not do anything. I want to know how to apply the rotation AFTER the tolerance values (on lens wedge, tilt, shift, etc.) are selected for each Monte Carlo trial, so that I can rotate the directional tolerances for the lenses in the first barrel with respect to the tolerances for the lenses in the second barrel. For example, if a lens in barrel #1 has a tilt of 0.062º +X in a Monte Carlo trial, I want to compare this with a  Monte Carlo trial where all lenses in barrel 2 have their previous tolerance values, but the lens in barrel #1 now has a tilt of 0.062º +Y/-Y/-X. 

Furthermore, is there a way to save the tolerance values for a Monte Carlo trial for use in subsequent Monte Carlo trials? I would also like to model the effect of swapping one set of (barrel #1 +  its lenses) with another set of (barrel #1 + its lenses), to compare which of the two barrels has a better performance when fit with barrel #2. 

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Best answer by Jeff.Wilde 26 May 2023, 02:45

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If I understand your question correctly, you can probably generate the tolerance results you are looking for without resorting to use of a tolerance script.  If you construct your lens train so that a pair of coordinate breaks surrounds your barrel 2 lenses (with the second coordinate break having pickups to undo the effect of the first one), then you can set up four configurations with tilt-about-z values of 0, 90, 180 and 270 degrees. 

Let’s say you have one field for simplicity.  When setting up the tolerance analysis, check the separate fields/configs option.  If you do use multiple fields, you will probably want to use the “User Defined” option. 

In any event, just run the tolerance analysis with whatever number of Monte Carlo iterations you desire.  If you then inspect the results in the Tolerance Data Viewer, you should find what you are looking for.  The criterion (say, spot size) will be reported for each of the configurations using the same set of element perturbations, the only difference being the barrel 2 lenses are rotated about the z-axis by the prescribed amount.  Here is an example using the Double Gauss 5-degree sample file, in which the last lens is rotated via a multi-configuration setting:

and the corresponding Monte Carlo tolerance results when only element tip/tilts were used in the tolerance data editor:

 

Regarding the last part of your question, you can have repeatable results if you use the SEED tolerance operand with a non-zero value.

 

Regards,

Jeff

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