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# Modelling an ellipsoidal volume in non-sequential mode

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Hello,

I just tried to create an ellipsoidal object in the non-sequential mode. I’m using OpticStudio 18.4.1. The only way I found is to use a FreeformZ object. Isn’t there a more straight forward solution? Like the toroidal or rectangle volumes.

Thanks in advance and with best regards,

Martin Jahn

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Best answer by David 25 August 2021, 02:12

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Userlevel 5
+3

Hi Martin,

It is possible to model ellipsoids in non-sequential using the Standard Lens. A bit of math leads to the relation ships below:

R = sy^2 / sz

k =  (sy^2 - sz^2) / sz^2

where sy is the semi-minor axis and sz is the semi-major axis

For the other coefficients of the standard lens

R1 is positive, R2 is negative (I use a pickup)

Clear1 = Clear2 = sy

Thickness = 2 sz

I did the math with Mathematica. I attach the notebook and a pdf. (It’s pretty readable.)

I also attach a zar giving several examples.

And my thanks to Jordan Teich from Zemax for disabusing me of a mistake in my thinking about the standard lens.

Kind regards,

David

Userlevel 5
+3

I really must learn to use Mathematica sometime. That’s such a nice exposition.

• Mark
Userlevel 5
+3

Thanks, Mark.  I’ve been using Mathematica for 30 years. I don’t know what I’d do without it.

It is perhaps worth mentioning that the same formulae can be used for ellipsoids in sequential mode, using two Standard Surfaces for each ellipsoid. The front face is the first surface and the back face is the second. The thickness is the thickness of the first surface and the clear apertures of both surfaces are the same. The convert to NSC tool works and converts the ellipsoids to the non-sequential form as standard lenses.

--David

Hi David,

thanks a lot. In the meantime I had the change to try and apply it for my specific problem. It works great.

Greetings,
Martin