Hi,
I am using paraxial lens as an objective to focus scanned light beam. Before I added mirror to the system, the paraxial lens was focusing, but after mirror was added, the light was defocused. I thought “quick focus” may help, but instead I got negative focus. What I am doing wrong?
Regards,
Marzanna
Best answer by Sean Turner
Black box surfaces do not work properly if a mirror is placed in front of them, unless the black box surface was created while the system was in mirror space (n=-1). If you compare to your post from last week where you had 2 scanning mirrors, the black box surfaces were behaving properly because after 2 reflections the black box surfaces were returned to n=1 space. Essentially, the black box surfaces will behave in whatever space they were created in, but not after an odd number of mirror reflections.
If you want to use these files with only one mirror prior to the black box surfaces, you will need to contact Thorlabs tech support and ask them to create some black box files for you where there is a mirror in front of the lens. They have done this in the past, but that was when I was the employee generating the black box files. I am no longer at Thorlabs, but hopefully somebody there can help you out.
As Zemax sign convention will reverse after putting a mirror into the system, there might be a possibility of sign convention mismatch after fold mirror, In case you have inserted the fold mirror manually, and adjusted the subsequent thicknesses and surface Radius of curvatures manually in your original design without fold mirror.
Try to add scan mirror using 'add fold mirror' option instead, so all subsequent thicknesses the radius of curvature will be adjusted automatically.
Hope this helps!!
Thank you,
That was my thoughts as well ( after I posted my question) however, the issue is that I am using black box files for scan and tube lenses, and their radius is either not stated or is just “Infinity”, but I will give a go with tips in your post.
Regards,
Marzanna
+1Black box surfaces do not work properly if a mirror is placed in front of them, unless the black box surface was created while the system was in mirror space (n=-1). If you compare to your post from last week where you had 2 scanning mirrors, the black box surfaces were behaving properly because after 2 reflections the black box surfaces were returned to n=1 space. Essentially, the black box surfaces will behave in whatever space they were created in, but not after an odd number of mirror reflections.
If you want to use these files with only one mirror prior to the black box surfaces, you will need to contact Thorlabs tech support and ask them to create some black box files for you where there is a mirror in front of the lens. They have done this in the past, but that was when I was the employee generating the black box files. I am no longer at Thorlabs, but hopefully somebody there can help you out.
Hi Sean,
May I ask another questions, pls? After determined the best, maximum scanning angels and calculating FOV, I would like to run spot optimization to see spot quality at different FOV area. Unfortunately, I cannot use the objective lens in simulation ( it is unavailable), instead I am using paraxial lens with the right focus length and magnification. Here are my questions:
I will be grateful for some tips.
Regards,
Marzanna
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