Leica DMLB Condenser

[Nebulous]

I was wondering if someone could help me identify some hardware parts and their functions so I can get a better understanding of what I'm working with and identify potential upgrade paths to pursue. As I mentioned in another post, the images in the Leica DLM* manual are really blurry so I'm not entirely confident on which part(s) they are pointing to most of the time. Without further ado:

• What condenser model is this? Leica has these two condensers in the manual DML* manual with S1 in the name: 0.90 S1 (BF, DF, PH (P) ICT 1.6x 1.35 mm) and P 0.90 S1 (BF, DF, PH (P) ICT 1.6x 1.35 mm). I also found Condenser head P 0.90 S1 in the DM6000 modular parts brochure which states "Focal intercept 1 mm, extremely low strain for all transmitted light contrast methods." I'm trying to determine what the pros/cons are of this particular condenser setup and what types of upgrades I can add with the current condenser.

• I looked up the part labeled "505091" and found it's an "opaque filter" which just looks like frosted glass. I've played with it a little bit by sliding the filter in and out and was able to achieve a pseudo-darkfield effect, but I assume this was just a happy accident with part of the filter frame cutting through the light source. What is the intended purpose of this filter?

• Are there other filters I can add to this slot? And what function(s) do they serve as partial or complete contrasting techniques? Am I correct in that you just pull the filter straight out to remove it and push it straight in? (I don't want to snap something by mishandling it)

• If I'm not mistaken, the two thumbscrews towards the front of the scope that are both attached to the same ring are for centering the diaphragm, is this correct?

• Are there any other mechanisms of this condenser I should know about aside from moving it up and down, centering, adjusting the aperture, and adding a filter to the filter slot?

• There is a third thumb screw on the right side of the first picture (above the right centering screw). What is this for?

• What are the purposes/intended use of the three filter switches DLF, N2, and grun (green)? DLF seems like a daylight filter. I'm not entirely sure about N2, but sometimes playing with it results in better contrast. And for the green filter, I read that the it's used to increase contrast for black and white photography and to manipulate light amplitude with phase contrast; not sure exactly how it serves me currently, but playing with the knob sometimes results in certain structures being more visible. Sometimes just tweaking each of these three knobs can produce some interesting results, but I have no idea what I'm technically doing.

• What parts would I need to upgrade to dry Darkfield? I assume based on my playing around with the opaque filter, I can do some basic DF with just a filter, but are there other components to Darkfield I should consider?

• What would I need to achieve phase contrast given my current setup? Does this condenser already support phase contrast and I'd just need objectives that work for phase contrast? Or are there other parts I'd need?

I bought this scope under the assumption it would come with basic Brightfield capability and that anything beyond that would be a bonus, but for all I know it's already equipped with other features (or parts to accommodate features) that I'm too new to identify. Thanks for reading

[PeteM]

Nebulous, I'm only seeing the first image. It's new to me but looks to be a step up from the standard condenser by having a slide-in and slide-out top lens to accommodate low-power (e.g. 2-2.5x) objectives. Could be wrong - you can easily see if it slides in and out.

The standard condenser has a slot that can accommodate a slide-in diffusion filter, polarizer, wave plate, or even a single-phase annulus. There's an eBay seller who has an aluminum replacement for the slide and laser-cut Delrin stopes and phase rings. Unfortunately, those will tend to melt if you aren't careful with condenser placement and heat - especially from the 30-watt versions of the DMLB with the lamp directly under the field iris. I believe yours is the 100-watt version with the lamp at the back. Despite the greater heat, it's placed at the back and will likely do better.

[Nebulous]

The images should load for you now Pete. I currently. have a 2.5x N-Plan objective equipped and I'm getting good clear results with it. Does that mean my condenser lens is only good for lower magnifications currently? I notice in most cases 2.5x, 5x, and 10x provide the only real usable images without making the specimen paper thin, and even then specimens with any level of transparency seem useless above 10x.

[PeteM]

Assuming I guessed right that the top lens slides in and out of position, you should have wide field coverage for your 2.5x objective with it out and excellent images at higher magnification with it in. You probably want to switch it "in" once you're at 10x and maybe even at 4x or 5x.

There should be a lever arm to move it. It's possible there is some dried grease and it's very stiff - in which case a bit of disassembly, solvent cleaning, and re-greasing should free it up.

If the top lens is not movable or otherwise not as guessed, maybe remove it to take a clear picture.

[Nebulous]

It does look like the lens slides along a track. I can take the condenser off and get some better pictures if that would help. I'm trying to be extra careful my first time taking things apart so that I don't unscrew the wrong thing and have the stage fall down and crack the field diaphragm or something haha. Maybe I'm just being paranoid.

I think this is the relevant figure from the manual, but I'm not sure if this is the same setup as mine—it looks like the third image has more circular attachments underneath the condenser head. Would you be able to point out the relevant hardware to detatch the condenser? Is it just the condenser clamp screw I have to look for?

No idea what the hole for guide pin, filter holder, or hole for attachment are. It's too blurry to cross-reference with my model not knowing exactly what part I'm looking for or if I'm even looking at the same model.

[PeteM]

There are typically two or three knurled screws holding the condenser in place.

You'll want to rack the stage up and the condenser down to get clear space. I'm pretty sure your model has a small one on the right side that fastens it to a carrier. (#5, Figure 5, on your diagram) Unscrew that. Then unscrew the two centering knobs, as needed, to take the whole thing out.

Just a couple drops of lighter fluid or other relatively safe solvent could help get things moving. Once you have it out and puzzle a bit, what you need to do to free things up should be clear. Directly sliding the lens, rather than using the lever, might help at first.

The threaded hole (#1, Figure 5, on your diagram) is for a swing-out polarizer. You can just use one over the field lens.

[Nebulous]

Pete — I haven't taken the condenser all the way out yet, but the lens is the slide-out version with the lever as you mentioned.

I'm looking at adding some polarization and darkfield filters. I watched MicrobeHunter's video on using linear polarizing filter paper for polarization as well as his other video on rolling your own darkfield. Any major cons to this approach versus buying something that fits to the scope? What would you recommend for supplies or premade parts on polarization/darkfield filters? I would prefer something that isn't completely flimsy like just transparency sheets and marker. In the diagram I posted (figure 1.3) there are also the three filters inside the body controlled by the levers—I assume before it gets to the field lens? (sorry if my terminology is off). Is there anything I'd ever want to modify in this area? I'm having a bit of analysis paralysis on how to proceed. And I always feel remiss not to say thank you again for repeatedely taking the time to help.

[PeteM]

For polarization, I suggest buying a decent-quality (so it goes to near full extinction) linear camera polarizer with a diameter that matches your field lens. It doesn't have to fit in or on the condenser. Should be under $20 or so on eBay.

You'll also need a polarization slider to fit from the side near the top of your stand. You might find one on eBay for around $100. You could also make your own - the slider out of plastic or metal, 3D printed or machined and then add a small glass linear polarizer to fit in a recess.

You could also drop a linear camera polarizer into the space between the head and stand, chosen to be a diameter that just fits. Circular polarizers can also be used if you orient them the right way, but spending the extra for a linear polarizer on the field lens and a linear polarizer (analyzer) above the objectives is likely worth the slight (in the came of camera polarizers) extra cost.

For darkfield, Saul and others offer a variety of darkfield and oblique laser-cut stops on eBay that are affordable. You can also cut your own out of any opaque material that is somewhat firm, cuts well, and is heat resistant. You can search the Web for examples.

[Nebulous]

I've seen several videos on making a DF filter. I'll probably experiment with making my own first to see how it looks with different configurations.

When you say I'll need a slider for the top, are you referring to the slot on the right hand side of the body just below the eyepieces? (Posted an image below) You wouldn't happen to have pictures or videos of your setup somewhere would you?

[PeteM]

The slider coming in at an angle just under the DMLB lettering is for a DIC prism. The one for the analyzer is at about the same height, on the left side (facing the microscope).

[wabutter]

This scope has a Dual view attachment below the viewing tube, so inserting an analyser is possible, but may require stopping down the eyepeice FN to 20mm if it is at 22 now. Depending on the viewing tube.

The condenser pictured is the 11501183 Aplanatic/Achromatic 0.9na. the P indicates Strain free so it is suitable for use with DIC. On the DM LB, the flip out position will support objectives from 1.6x to 5x. The 11555091 is a diffuser glass for use in the low mags. Koehler illumination is supported from 10x up with out the diffuser and with the top element in place.

There are two ways to implement an analyser into the system. 11551071 is the Pol Module, that has an analyser and Bertrand lens included in the piece. An alternative is the Analyser mount 11505121. It would also require the analyser slider 11555045.

Dry Dark Field requires 11505075 Dark Field Base and 11505076 DF top element. Add the immersion tope element 11505075 to the base. High mag objectives may require a iris diaphragm for the best contrast. Usually over 40X

Alternative slide inserts for the condener are: 11555068 full wave compensator for use in Pol Microscopy. 11501158 DF slider; 11501155 PH1 Slider; 11501156 Ph2 Slider; 11501157 PH3 Slider for phase. and the aforementioned 11555091 diffuser