Posted by
mmodel on
URL: http://confocal-microscopy-list.275.s1.nabble.com/Wide-field-Epi-illumination-overfilling-the-aperture-tp7587113p7587115.html
*****
To join, leave or search the confocal microscopy listserv, go to:
http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopyPost images on
http://www.imgur.com and include the link in your posting.
*****
Dear Lu,
In practice, we focus the collector lens at whatever plane gives us the best combination of uniformity and brightness. But it is never perfectly flat across the field unless, as George McNamara said in his post, you use a scrambler or something. I suppose that by simply projecting something as variable as mercury arc you cannot expect to get perfect illumination.
Mike
________________________________
From: Confocal Microscopy List <
[hidden email]> on behalf of Yan, Lu <
[hidden email]>
Sent: Friday, August 4, 2017 12:45 AM
To:
[hidden email]
Subject: Wide field, Epi illumination, overfilling the aperture?
*****
To join, leave or search the confocal microscopy listserv, go to:
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Flists.umn.edu%2Fcgi-bin%2Fwa%3FA0%3Dconfocalmicroscopy&data=01%7C01%7Cmmodel%40KENT.EDU%7Ca9ba5fb033a34939f9d708d4daf3d3ad%7Ce5a06f4a1ec44d018f73e7dd15f26134%7C1&sdata=wbx4UwbUCyfd7kwJdrd5n%2FnGXlDKROgBspzdg4o0igM%3D&reserved=0Post images on
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.imgur.com&data=01%7C01%7Cmmodel%40KENT.EDU%7Ca9ba5fb033a34939f9d708d4daf3d3ad%7Ce5a06f4a1ec44d018f73e7dd15f26134%7C1&sdata=B4%2BxjBLa9gf30TE7Uy4np07eadfth81QXu0vG9qbOqk%3D&reserved=0 and include the link in your posting.
*****
Hi,
I was searching for back aperture (or exit aperture plane) and the back focal plane of high NA objective lenses, and found this thread that Kyle posted in end of 2015:
https://na01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fconfocal-microscopy-list.588098.n2.nabble.com%2FObjective-back-focal-plane-vs-exit-pupil-plane-locations-td7584559.html%23a7584565&data=01%7C01%7Cmmodel%40KENT.EDU%7Ca9ba5fb033a34939f9d708d4daf3d3ad%7Ce5a06f4a1ec44d018f73e7dd15f26134%7C1&sdata=N9twDfsIfwM4sXG6QVDH2%2FbyDzlxxjN%2BzQgEcrr4trA%3D&reserved=0, in which all agreed most of cases, these two planes are not coplanar.
I understood that, for confocal scope, one would want to 'overfill' the back aperture of an objective, as described in several textbooks, to utilize the full NA of the lenes, and achieve smallest spot size possible. There, since the laser beam comes in collimated, it of course also overfills the back focal plane which often lays inside of the objective lens (I found this website providing Zemax models of several Nikon lenses based on publicly released documentations:
https://na01.safelinks.protection.outlook.com/?url=https%3A%2F%2Ffigshare.com%2Farticles%2FZemax_optical_design_files_of_microscope_objectives_tube_lenses_and_Fourier_imaging_setups%2F1481270&data=01%7C01%7Cmmodel%40KENT.EDU%7Ca9ba5fb033a34939f9d708d4daf3d3ad%7Ce5a06f4a1ec44d018f73e7dd15f26134%7C1&sdata=cGMeYj3U8Twi0kiG2dOcGXeZN1TVADipZ%2F1zZKm33QA%3D&reserved=0 ). I have simulated several of them, and found that the 'back focal plane' is indeed residing inside of the lens. Some of them are actually almost in midway of the lens housing.
Based on these information, I was wondering, for wide field scope, epi-illumination (non-critical illumination), what would be the best practice to choose the relay lenses to focus onto this back focal plane to get most uniform, and possibly large illuminated FOV, considering there is a hard stop up stream, i.e. the exit aperture of the lens. It seems to me that depending on the distance between these two plane, and the size of the exit aperture, there is a limited NA for lens that focuses the collimated laser beam onto the back focal plane. Is there an 'overfilling'-equivalent concept for epi-illumination? Does it matter if one comes with quite large cone angle to focus onto the back focal plane, and the beam is clipped by the back aperture of the objective lens? Would the amount of clipping affect the illumination quality in general? I guess this kind of clipping will play more important role in TIRF or SIM case where one wants to focus beam(s) onto the edge of the back focal plane of the objective. Smaller cone angel will give you small beam size (collimated) on the sample plane), but large cone angle will be clipped by the back aperture of the objective. I am trying to collect all relevant thoughts from experts here on the list, and any inputs will be welcome. I have to get several concept clear in my head.
Thanks,
Lu