Leitz Dialux II: add phase contrast?

[uski]

Hi there!

Alright, alright, here is a question for the microscopy geeks among us. I have a Leitz Dialux II microscope, with a condenser that can't accept filters as-is, let alone phase contrast rings. But, I do want to add phase contrast. It's driving me crazy to not have it.

Based on previous experiments, I think it might be possible. Here is what I found:
- https://www.micromagus.net/microscopes/diyphase.html
- http://www.microscopy-uk.org.uk/mag/art ... phase.html

I have access to a 3D printer and a laser cutter, so I can manufacture or cut very precisely.
But I am new to microscopy, and lack some optical knowledge. That's where I need your help!

1. In theory, if I design a filter holder that attaches to the bottom of the condenser, would it work ?
2. If yes, how do I figure out the optimal dimensions for the phase rings ? Surely there must be a way without trial and error, which seems basically impossible due to the high number of combinations.

Another option might be to adapt a condenser from a Laborlux D, model 56, BUT I do not know if it is compatible. IF it is, I can add filters with phase rings, so that's perfect. Any idea if it would fit? It seems like I need to change the condenser carrier - the change does not seem obvious at all but maybe someone knows if it can be done.

I got myself a Leitz 40x 160mm Phaco 2 objective to experiment.

Any pointer would be very much appreciated. Thank you!

PS Of course if I can get my hands on a suitable phase contrast condenser, that would be awesome, but, they seem unobtainium or those for sale are either overpriced or broken or miss parts...

[blekenbleu]

As nearly as possible, condenser phase contrast filters should be in the same plane as its diaphragm.
With a centering telescope or Bertrand lens,
adjust the condenser diaphragm to match the objective annulus, then measure the diaphragm.

[PeteM]

It should be possible to insert a laser-cut annulus in the standard Dialux condenser, one at a time, in a manner similar to the design Saul (a member here) does - since there is a cylindrical opening at the bottom and room to get near the iris. He might even be willing to make up a set, if he doesn't do so already.

Simplest and best approach -- but more expensive -- would be to look for a Leitz 402a phase condenser and the corresponding Leitz phase objectives. They sometimes show up for not so much money. The only one currently on Ebay is $299 plus tax and shipping, but in time one at lower cost should show up. This will have precisely made phase rings. a darkfield annulus, and a flip top lens that will perform well from low to high magnifications. Like the Dialux scope, it's very well made.

The slightly newer Leitz Laborlux D phase condenser is not compatible - it uses a larger dovetail to secure it and sits higher above the carrier. It wouldn't be trivial to properly retrofit it, even for someone with a fairly complete metal shop.

In most cases, you can use either Leitz 170mm or Leitz 160mm finite phase objectives on the referenced Dialux - the phase rings often match up. You do have to use the older eyepieces and be prepared to have things not parfocal below around 16x objective magnification if you use the newer 160mm phase objectives.

FWIW, I suspect "Dialux II" was just that site's way of distinguishing the older black painted Dialux from the newer gray painted ones -- and not a terminology Leitz itself used. In any case, the pictured model typically had 170mm tube objectives (though it can support most newer ones). Newer models (Dialux 20,22 . . .) had different heads (42mm vs. the older 43mm dovetail size) and were meant for 160mm tube length (DIN standard) objectives . . . with microscope paint colors that migrated from black to gray to off white.