Spot size inconsistencies between the designs with the same lens
Hello,
I created an optical system using Thorlabs collimator RC08FC-P01 (90 degree reflective mirror) and AL2550M lens. The Zemax files were obtained from Thorlabs site and modified to fit my needs.
If I only use a lens as designed by Zemax engineers, the spot size for 405 nm is 0,15 microns, but if I use a collimator and then put the lens in the beam path, the spot size for the same wavelength is much larger at 55 microns.
Is this due to design of collimator, software artefact or something else?
I attached .zmx files of the lens and collimator+lens designs.
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@pepe
AL2550M-Zemax.zip only contains a session file (*.ZDA). In general, when sharing design files, it is better to save an archive: File..Create Archive (*.ZAR) and ZIP it before uploading it to the community.
That being said, I think I found the issue.
Although you changed the radius and thickness of the Even Asphere Surface 11 to be negative (mirror space), you didn’t change the sign of the 4-8th order terms. If you change the signs of those parameters to be negative and do a quick adjust of the focus you get:
Which is probably closer to what you’d expect. If you use Librairies..Lens Catalog..Insert, there’s a checkbox that let you select Change Sign of Surface Geometry in Mirror Space, if this is clicked, and you select AL2550 from Thorlabs and insert this lens after a mirror, you’ll see that the terms are all negative:
I hope that makes sense.
Take care,
David
@David.Nguyen
OK, I will make sure to follow the procedure you suggest for uploading the files.
And a huge thank you for posting a solution to my problem. It makes a lot of headaches go away.
@pepe
No worries, don’t forget to mark the post as answered if this is solved.
