Perhaps you will find this useful.
On our confocal systems, especially with the microscope enclosure, it has been really difficult to set the correction collar to a desired value because the markings are hard to see and one cannot really get close to read it comfortably.
Especially with multi-immersion objectives, I advise users to always verify the settings at the start of their session.
So I ended up using a cheap USB endoscope camera ($25 on Amazon) that is positioned below the stage and shows the objective on the computer screen. It is now quite easy to see the settings, without having to stick your head inside the microscope enclosure.
I have recorded a short video showing its operation.
I am aware that the truly correct way would be to tweak the correction settings while imaging the sample, but accessing the collar while the sample is on the stage is impossible (I love our motorized correction 40x objective for that reason).
Microscopy and Imaging Center
Texas A&M University