Olympus IMT-2 phase annuli focusing and aligning problem

[Rorschach]

I am working on setting up two used Olympus IMT-2 phase scopes that my unit recently bought used. Both have the ULWCD ultra long working distance phase condenser with all the proper phase annuli and the four original phase objectives (4x, 10x, 20x and 40x).

I am not able to focus on the annuli for some objectives using the built-in Bertrand lens (it is activated by one of the mag changer's three positions, the other positions are 1x and 1.5x). Like at all. When I remove an eyepiece, I can see the annuli but too "far away" and not precisely enough to align. I don't have a phase telescope with me here and the method of using two eyepiece seems not helpful (I tried).

A further problem is that the two screws on the condenser that are for aligning the phase stops don't seem to work consistently. I can move the stop to a few directions but not to every direction, which obviously is problematic. Also this problem exists on both scopes.

Maybe I am doing something wrong as these problems manifest on two identical scopes?

In bright field everything works as it should on both scopes: nice crisp image using all objectives.

[MichaelG.]

I don’t think I can help regarding the first problem … but perhaps with the centring adjustment

here’s a photo of my two adjusting screws !!
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IMG_9342.jpeg (201 KiB) Viewed 264 times

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The little inserts are 3mm diameter, and appear to be made from something like Acetal/Delrin
… sourcing suitable material in small quantity, at a realistic price, is proving difficult.
but other matters have taken precedence recently.
MichaelG.

[FredH]

When I got my used IMT-2 I think it had the same problems as yours. The phase mask centering adjustment mechanism was very sticky. It was pretty straightforward to take it apart;

Condenser_Carousel_1.JPG (145.66 KiB) Viewed 244 times

Taking off the cover plate allowed removing the phase mask units

Phase_masks_removed_from_Carousel.JPG (163.71 KiB) Viewed 244 times

Brass_pushers_for_phase_ring_adjustment.JPG (54.09 KiB) Viewed 244 times

The adjustment screws push the phase mask units against the spring-loaded brass cone-tipped cylinders seen in the photo; these were mostly locked up due to dried grease. One of them took some heat to remove, but they cleaned up nicely. I also cleaned some dried grease from the recesses that held the phase mask units. The adjustments worked fine after that.

My Bertrand lens adjustment was also gummed up; it would focus on the x20 objective phase ring but not on the x40 objective phase ring. I left the scope sitting around for a year or so to age; by this time the Bertrand lens focus adjustment wouldn't move at all. My attempt to fix this was more stressful and less successful.

bottom_with_balls.JPG (153.97 KiB) Viewed 244 times

Once I got the assembly removed from the microscope body I found that removing the four screws shown sets free the 106 ball bearings you can see in the photo. However, they are held in place by very sticky grease and I'm pretty sure I didn't lose any. After setting aside the balls, I flipped the lens carousel over and removed the three screws from the top plate

Top_showing_Bertrand_lever.JPG (88.47 KiB) Viewed 244 times

(The big ball in the center is loose and is just held on with grease in this photo).

Taking off the top plate reveals the Bertrand lens focus actuating lever, which was unmoveable. After reading a post about MichaelG's success with a heat gun, I tried a heat gun and got the Bertrand focus to move pretty easily, then put things back together. I cleaned the old dried grease from the focus rack and installed the unit back in the scope. However, after a few weeks the Bertrand focus moves only stiffly, and now I find that I have annoying slop/hysteresis in the focus, so I've set the microscope back on the shelf to age some more.

So, if your scopes have the same problems as mine, I would recommend cleaning up the condenser carousel as I did, but if your Bertrand lens is sticky, I'd maybe just try gently applying a heat gun without removing the assembly.

[Rorschach]

FredH, many thanks for the info and the photos, extremely helpful! What you describe sounds exactly like what I am having here.

I will likely forget the Bertrand lens in both scopes now and in the future. Having a phase telescope should be enough.

The phase mask mechanism I will try to fix later on on both scopes. However, right now there's no time for such a big job so I'll just replace the condenser on one scope with a spare LWCD condenser that we have (became a spare when that scope was upgraded to DIC) and the other symptomatic scope will be for just brightfield for the time being.

Edit: MichaelG, I hope I don't find what you showed in the photos, when I do open up the condensers!