looking for "us_gskew.dll" from skew rays to model Gaussian beam propagation webinar

  • 14 September 2023
  • 3 replies


I’m looking for “us_gskew.dll” shown to be used in “Using skew rays to model Gaussian beam propagation in OpticStudio” webinar.

I download the attached zip files which contained *.c file. I wonder where can I find the complied file. is there a reasone why I couldn’t used an allready complied filed? (and instead have to complie it myself)

Thank you,



Best answer by Jeff.Wilde 18 September 2023, 18:41

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Userlevel 7
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Hi @amir,


I’m attaching mine for you to try (there’s no guarantee it’ll work, and even if it works the code could have been changed in between as I’ve downloaded this long time ago), but I think there are several reason why its better to compile it yourself. Its not a difficult procedure, and its described in this Knowledgebase article:

One important reason why you want to compile it yourself is that there could be nefarious code in the DLL. Whereas if you were to compile it yourself, you could double-check what the code is doing beforehand.

The other important reason, as I stated before, is that if someone modifies the code, they don’t always update the *.DLL. Its essential to make sure you have the right version of the code, and having the source code helps you understand what the DLL does exactly.

The other reasons have to do with how the DLL was compiled in the first place. I’m not an expert in this, but I think it could have been compiled for 32-bit, and when you try it with a 64-bit machine it wouldn’t work.

I hope this helps.

Take care,



Userlevel 7
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The dll version is included in an archive file.  For example, if you open


then the dll will be automatically added to the appropriate location.


It looks like us_gskew.dll is about 10 years old, which is when the code was originally written (according to a comment in the source file):



Even so, this version seems to work okay on my 64-bit machine.


Thank you David and Jeff,

I tried the solution Jeff suggested and it worked like charm - just opening the skew_opt_with_UDS_paraxial_lens.zar file and the DLL was copied to my Zemax folders.

Thank you,