olympus CH2 phase contrast help

[rolf]

Hello. I'm new here and I recently purchased an olympus CH2 with a phase condenser (see pic). I can't find this condenser on the internet and it doesn't match the pics in the CH2-PCD-PL manual that came with the scope. Any ideas price/history/use? It also did not come with any light filters and as I am new to phase contrast I wonder if I should get some and how.

I have played with it a bit and I see that it does something but I will need to learn and explore more.

Any help is much appreciated.

Thanks,
Rolf

[Charles Krebs]

Rolf,

Do you have any instructions at all about setting up phase contrast? It is not that tricky. The primary thing is that the condenser must have annular diaphragms that "match" the phase plate that is built into the objective. If you have Olympus phase contrast objectives and an Olympus phase contrast condenser from the same "era" this should be fine. (There is no cross-manufacturer compatibility, although on rare occasion, it might work mixing different manufacturers phase contrast equipment)

You do need to select the correct phase annulus in the condenser to match the objective (These are typically marked something like “Ph1,” “Ph2,” or “Ph3” to designate the different sizes). Then, there will be a fine adjustment on the condenser that allows you to move the phase annulus in small amount so as to line up the "circles" in the condenser and the objective. In order to do this an eyepiece must be removed, and you look "down" the eyepiece tube. Normally another optic... a "phase telescope" or "Bertrand lens" is inserted temporarily in place of the viewing eyepiece to magnify these rings (at the objective's "back focal plane") and make the alignment process easier. But if you don't have one you can usually still do it by "eye" if you can focus closely or have a pair of strong reading glasses. Once these rings are aligned you should observe the phase contrast effect when viewing a specimen.

[rolf]

Wow, Charles Krebs! I'm honored, thanks for the reply. I do have some instructions and I believe I have gotten the hang of it. Diaphragm has settings of 0, 10, 40, and 100. Objectives are for phase contrast as well - A10PL, A40PL, A100PL. I have read much online about the physics of the light and the technique.

As for finding this exact model of condenser online I am still looking, but I don't think not having that info will hold me back. Olympus material is scarce on these older models, but I would still like to get an idea for resale if I ever scrape up the difference for a DIC scope.

I'll have to focus on the photography now. Thanks for explaining your setup and techniques on your site.

Thanks again for the response and please keep up the stellar photo work.

Cheers,
Rolf