How to perform tolerancing with composite surfaces

Question

Hey friends, I am wondering how to set up tolerancing using composite surfaces.

Basically, I have a composite surface configured with the designed curvature of a lens as the base, and the Grid sag file generated based on errors I measured from a lens using profilometry. I would like to see if I have multiple times of the error adding on the base, how bad the lens performances will be. I was trying to use TIRR but I was confused about how to set it up. Can anyone suggest? Tutorial on ‘Tolerancing irregularity with Composite Surfaces’ was not very clear on this to me.

Erin.Elliott · Accepted Answer

Hi! You can use a stack of Composites to add any number of errors to your surface. Stacking composites in this way is handy for tolerancing positions or mount effects on as-built optics, among other applications.

You can put multiple GridSag surfaces in a stack, and turn on the Composite property for all of them. This will sum all the GridSags onto the surface following the composites.

If you want to also add random irregularity terms, you can insert a Standard surface into the stack, as well, and run TIRR, TEZI, TEXI, or ISOB operands on the inserted surface. Here’s a pic of how that might look:

When you run tolerancing and generate Monte Carlo files, the “Standard” surface in row 5 will be changed to a “Zernike Standard Sag”, and the Zernike coefficients are used to add the additional surface irregularity. To see this, set up tolerancing to save a Monte Carlo file so that you can take a look at the file later:

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