Hi Jake,

I'd suggest checking the tolerance settings. Run the tolerancer manually, and load the TOLRxxx.TOP file that holds the settings fo rthe analysis. How long does that take?

- Mark 

Hi Jake,

Set up the Tolerancer as you want it to be, and then press the Save button on the Settings dialog. Save the settings to a file called TOLR***.TOP where *** is an integer between 001 and 999. Then when you call TOLR in the merit function, you refer to the *** integer to tell OS what settings to use.

There's a good Knowledge Base article here: https://my.zemax.com/en-US/Knowledge-Base/kb-article/?ka=KA-01370 :-)

Much as I love TOLR, I think the new HYLD approach beats it in terms of coming up with designs that are insensitive to tolerances.

- Mark

Hi Jake,

Can you share your file as a ZAR? Then we can see what's going on.

Everything pushes the design to its maximum length. That's why we usually just set a maximum length, rather than optimize to obtain some other length where performance drops on either side. 

Hi Jake,

OK, I have a couple of thoughts on your (very complicated!) system.

1. You are using Paraxial f/# as the aperture definition, which is fine for initial setup. But you can't use it for tolerancing. Imagine some tolerance that changes the f/#: OpticStudio will compensate for the tolerance by changing the ray it traces to ensure the f/# condition is met. That's not what you want. Switch to Float-by-Stop so the aperture is defined by the diameter of the stop surface for tolerancing. That's the physically realistic case. Note the Design Lockdown tool does this for you, and should always be used as you move from optimization to tolerancing. Of course, you want to use tolerancing in the optimization, so you're not ready for the design lockdown tool yet. But you should still set the aperture by the system aperture size directly, and use an operand to control the f/# when you want to tolerance.

2. Your tolerancing crirerion is diffraction MTF (which you said in an earlier post, and I failed to see). That simply is going to be a big calculation, especially as it is set to sampling =4, or 246x256 grid. That's going to be a BIG calculation, and if you have n variables you will do it n+1 times per optimization cycle. Instead, for tolerancing purposes, use RMS Wavefront. You'll get best MTF near to where the RMS wavefront optimizes anyway, but it will be much, much faster. I made that change (and the change to aperture) in the file you sent me and it is attached.

3. In your even asphere surfaces, you are using R and k and the r^2 term of the Even asphere. (R, k) and the r^2 term are degenerate, so you should only use one (R&k) or the r^2 term. I suggest you go back to an earlier version of the file, set all the r^2 terms to zero and don't set them as variables. It's making optimization needlessly complex.

4. You're using TOLR data 0, which is the expected change. Its possible to find a design with poor performance but low tolerance sensitivity, and that's nott he solution you want. I suggest you use data item 2, which is the nominal + expected change. This is the number you want to have as small as possible.

5. Last, and you probably know this, be very careful using paraxial quantities when you have such wildly aspheric surfaces. Paraxial quantities are computed using R, k and r^2 only. The features in Analysis...Applications...PAL/Freeform are very useful in cases where paraxial quantities can't be relied upon. Always use calculations based on real ray tracing when modeling wildly aspheric/freeform surfaces, as the surface vertex power has little to do with the power over the aperture of the surface.

Lastly, if I may sound like an old geezer, back when I were a lad optimizing a zoom lens was something that took days/weeks of time, so don't be too harsh on the time TOLR takes. If you have n variables, it is doing n+1 Sensitivity analyses per optimization cycle. It's a very, very big calculation.

 Hope that helps,

- Mark

Hi again,

A followup question to one of your points you've made -- is it advised to match the optimization criteria to the tolerance criteria? For example, if I set the tolerance criterion as RMS wavefront, would optimizing for wavefront produce a better imaging system than optimizing for contrast?

-Jake

Hi Mark,

Thank you for your suggestions and insight, I will see what I can do!

-Jake