MicrobeHunter.com Microscopy Forum

I recently discovered an old "American Optical Fifty Phase" microscope that had been stored away for many years. It is monocular and has a " filter wheel" where the diaphragm would be on a typical scope. The wheel has four settings labelled with a white, a green, and a yellow-green bar, and one with a white triangle. It has a 45 x dark phase objective, a 10 x dark phase objective, and what appears to be a normal 4 x objective. Below the "wheel" is a toggle of sorts that appears to switch between a red and green filter.

I never received any training on what I believe is a phase contrast scope. Do you know what the labels on the wheel represent and what the red and green filters do, or can you point me to resource that would useful? Many thanks!
KB

KB,
Hey! Sounds just like the AO fifty phase microscope that I have!
Only difference on the one I have, no red filter on the toggle switch, just green and clear.
On the base plate (the part to remove to replace the lamp) has Model 60,61,62.
Could not find any info on the AO fifty anywhere, searched through the 107 AO microscope manuals etc. DVD. Could not find any info on the person who put it all together other than his name is Michael.
Only mention of the turret you described is from the AO 151 Phase contrast microscope listing:
Hope these pictures help you as much as they helped me, because there is no way with just words to describe alone.
Used snip tool to capture in two parts, hope it helps.

V

Thanks for pointing!

The color codes on the rotating ("Zernicke type") phase condenser correspond to the phase contrast annuli inside - and as noted above should match up with the phase contrast objectives color banding you have.

This is one of the most affordable phase contrast scopes available, but with an old illumination system that's a bit too dim for 100x in brightfield and maybe 40x in phase contrast. Shouldn't be difficult, however, to convert it to a brighter LED lamp.

I'm still confused by what you mean by a "Zernicke Type" phase condenser , Pete. Just what exactly is that?

It's an homage to Frits Zernike, who won a Nobel Prize for what most makers now call "phase contrast." It's also used, by several researchers I know, to describe the rotary type phase condenser with multiple phase annuli in it -- perhaps because that's what most post-WWII makers ended up providing when makers finally rushed (after a decade or so of mostly ignoring Zernike) to commercialize it?

An homage..... Since as you say, Fritz Zernicke invented phase contrast would it not be accurate then or in fact a better homage, to refer to Zernicke type phase contrast as a system that is similar in design and function to his original embodiment?