Determining the back focal plane of an objective

[onilink_]

Hello,

Is there a simple method for determining the back focal plane of any 160mm biological objective?

I have an Olympus BH2 and it seems that my magnification changer has a Bertrand lens.
Would that be useful?

Thank you

[dtsh]

I am not the most conversant with this stuff but my understanding is that from the back focal plane the condenser iris, filament, and rear focal plane should all be in focus.

When looking through the scope of course the field iris, specimen and the objective's iris if it has one should all be in focus.

Given that, I think if you stop down the condenser iris to be visible, when it is in focus you should be at or near the rear focal plane.

As for the utility of a Bertrand, they can be very useful.

If you pull an eyepiece and look down the tube, you should be able to see the rear focal plane; albeit not well, but the condenser iris and other items should then be in focus.


https://www.microscopyu.com/microscopy- ... microscopy

Corrections to any misunderstanding welcome.

[onilink_]

Thank you for your answer dtsh!
I'll try to experiment with that.

[MichaelG.]

It doesn’t answer the question explicitly, but your will find 17 occurrences of the term here:
https://www.iso.org/obp/ui#iso:std:iso: ... :sec:3.1.9
and collectively they explain.

I am posting that link because it’s very rare to get a freebie from a Standards Organisation !

MichaelG.

[onilink_]

Oh it's really a great piece of documentation, with lots of terms I didn't know.

Thanks a lot!

[viktor j nilsson]

The method described by Paolo Pozzi in the thread below is the best I've found:
https://www.researchgate.net/post/Is_th ... ctive_lens

I've used it to measure the location of the back focal plane of a bunch of Nikon MPlan objectives, as I wanted to deduce the characteristics of the DIC prisms designed for them, described here:

https://www.photomacrography.net/forum/ ... 45#p285745