Hi Steve,

I took a look at the 54087 file in Sequential Mode and played around with the Convert to NSC group tool. 

It seems that, as is, the model has this shaded-off region, and whenever it’s visible, the conversion doesn’t work well, and it throws the toroidal sag error. 

If I change the thickness to be anything larger than 2mm (I’m using 2.0000001mm), I am able to convert it to an NSC file without the error. 

So, considering that the Diameter is given as 2.00 +0.00/-0.03 on the EO site, and something like 0.0000001mm (1 Angstrom) is far below the tolerance given in that spec, I think you should be fine to do this while simulating your system.

In conclusion, try out setting the thickness of surface 1 in sequential mode to 2.0000001, or whatever you find acceptable to fix the model, and convert it to an NSC model. 

Here’s a KB article on how to use the Convert to NSC tool : Converting sequential surfaces to non-sequential objects – Knowledgebase (zemax.com).

Let me know if this works for you! Or if anyone else has more comments on this, I’d love to hear it! 

Hi Nikki,

Thank you very much for your method to fix the issue I had. I repeated the process you described and was able to convert it to the NSC model without any errors. It was very helpful. Thank you very much.

In my design, I need to optimize the Rod lens parameters to meet my design requirements. It was nice to find out what causes the shaded-off region and what causes the "Invalid Toroid Sag" error. If you or someone else have more comments on this, I would greatly appreciate it.

Regards

Steve