Hi Tiffany

I think that it is quite equivalent to tolerancing. The point to figure out is what does the lambda/4 mean? Is it a peak-to-valley error, is it a RMS? What would model best this error? This comes down to how it is measured and how it is manufactured.

To tolerance the irregularity in OpticStudio, there are basically two choices: model the irregularity as a sum of spherical and astigmatic terms or model the irregularity with a Zernike surface.

In both cases, you can apply that error on the beamsplitter surface and then run the tolerancing. I have attached an example.

If you add a SAVE operand in the tolerancing, it will save the system at - tol and + tol.

The files are saved in the same folder as your file and they are called TSAV_MAX_0001.ZMX, ...

For more information on the Zernike terms, have a look at those articles:

How to use TEZI to tolerance for manufacturing-related surface sag error

Constructing mid-spatial frequency tooling errors for evaluation and tolerancing

and this forum thread:

Tolerancing- understanding of when using TEZI, the max tolerance value is RMS error of surface

Sandrine

Hi Tiffany,

You can also use a Zernike surface to pre-aberrate the beam by a known aberration. Se  https://my.zemax.com/en-US/Knowledge-Base/kb-article/?ka=KA-01392 for an example.

The problem is that while people will tell you that the compoent is 'flat to lambda/4' or whatever, you need to know how the aberration is distributed. If it's a nice low-order focus error then it can be easily compensated by a focal shift, and the higher-order and less-rotationally-symmetric the lambda/4 is, the less you're able to correct it.

HTH,

- Mark