Zeiss Epi Turret and Nosepiece For Universal 1st edition

[colinbm]

I have added an old Zeiss Epi Turret and Nosepiece For Universal 1st edition to my photomicrography rig.
It came with four Epi objectives.

Epiplan 2.5x0.08

Epiplan HD 6.3x0.16

Epiplan HD 16x0.32

Epiplan HD 40x0.65

 

Yellow butterfly wing scale taken with the Epiplan HD 40x0.65, it only has a WD of 0.1mm.
I managed a a stack of 17 photos at 1.25um steps.

 

I will wait for some M24 to RMS screw adapters & try with the 100x finite objective & see if it is clearer.

[Nate]

Nice setup Colin.  I don't know much about these setups, is that a light in the optical path?

Almost looks like an ADC corrector in there too.

[colinbm]

Thanks Nate

The light on the side is called Epi-illumination & via a 45deg mirror allows the lighting through the objective.
Good for higher magnification when reflected lighting is too tight.

[Nate]

Ok that makes sense, thanks 

[enricosavazzi]

On 3/30/2023 at 5:35 AM, colinbm said:

The light on the side is called Epi-illumination & via a 45deg mirror allows the lighting through the objective.
Good for higher magnification when reflected lighting is too tight.

Colin and I briefly discussed epi-illumination with Zeiss BD objectives on photomacrography.net. I am currently busy on a project of doing something similar, albeit with Olympus infinity-corrected BD objectives for photomacrography of three-dimensional opaque subjects. In my case I will be starting at 50x and probably go a little higher. BD means epi-Brightfield + epi-Darkfield, it is a general term, not just a Zeiss "thing".

 

A few of these Olympus objectives have been discussed on photomacrography.net, but as far as I am aware, these objectives have always been modified by unscrewing or cutting off the front of the outer barrel (i.e. the illumination sleeve) and the subject illuminated by external light sources diffused by a cylinder of diffusing film placed around the subject or around the inner objective barrel. Colin seems to be the only one I am aware of, who wrote about using an epi-illuminator designed for these Zeiss BD objectives in photomacrography. This is essentially the same thing I will do (or at least try out) with my Olympus equipment. In addition I will also try epi-brightfield illumination, which can be used also with non-BD objectives. I have a couple of ideas on how to make both types of illumination more directional than the completely non-directional illumination produced by BD illuminators. It's not that difficult and there are probably multiple ways that work.

 

I do not plan NUV or NIR illumination at present. NUV is probably not transmitted by the BD illuminator, anyway (it is quite bigger and optically more complex than the simple Zeiss illuminator). I already have 2x to 20x on a Mitutoyo industrial microscope, so I am already covered up to 20x. I am currently assembling and modifying an Olympus modular industrial microscope for this project, mixing and matching a Frankenscope-like combination of parts from different generations of Olympus microscopes. The turret of my Mitutoyo FS-60 is already full of objectives and the Olympus objectives cannot share turret places with the Mitutoyos, they are just too different in multiple respects. So this project is not something that will be finished in a couple of weekends, and the end result will be a complete, additional microscope.

 

For now, just a picture of the microscope turret. Why two 50x objectives with very different NA and WD? That will be part of the story (spoiler alert: it is not just for testing both and deciding which one to keep). And yes, the BD objectives are that "fat".

 

[colinbm]

Thanks Enrico, good luck with your project.
The Zeiss Epi turret didn't work out as the mirror is degraded & I haven't been able to disassemble it as the screws have been glued in.
I have also tried a Co-Axial lighting but I haven't has any success with it as it is like looking through smoke ?

 

[enricosavazzi]

Yes, coaxial lighting/epi-brightfield tends to give a very flat ("rabbit-in-the-headlights") illumination and is very sensitive to dust and damaged coatings in the microscope objective and illuminator. However, with a high-NA objective it may be possible to use an asymmetric illumination across the optical path, in order to provide some shadowing, at least in theory. A thin light guide placed de-centered close to the beam splitter in the illuminator head might do the trick, or a small asymmetric field stop in the illuminator. How well it works in practice remains to be seen.

An oxidized epi-darkfield mirror (the one around the rim of the objective) can also be a problem. One thing that might be possible is unscrewing the front epi mirror of the objective and have it electroplated with chrome or aluminum on its interior surface, to restore some of its reflectance. Perhaps even coating its surface with a thin aluminum kitchen foil might do, for objectives with a long WD.

 

In the end, if neither illumination type works, we can still chop off the front of the objectives like others have done, and live with whatever illumination we can supply sideways with an external source.

 

[colinbm]

Thanks Enrico
I am probably expecting too much ?
But I just want to see down the holes in the beetles shell & the ribs in the butterfly wings.
With the 100x objective, the lighting is mostly horizontal.

 

PS. some metallurgical microscope specifically state they use plain glass in the epi-illumination.
I might try this, as it is an easy thing to do on the Co-Axial light I have.

 

[ulf]

If you are aiming at seeing the structures like the ones in the link below, just after the title "THE BLUE PARADOX"

https://roboticamoeba.com/2016/03/02/structural-color-the-butterfly-wings-iridescent-secret/

Then I think you are expecting too much.

 

The SEM images at 20 000x magnification hint that the individual ridges are maybe 300nm wide.

As your illumination wavelengths are longer those are out of reach.

 

I think that the second grey (b) image also is a SEM image with less magnification.

The 5um distance bar covers four ridges and three groves.

The hint of the much smaller structure in the groves in that image would not be possible with visible light.

They are far smaller than the wavelengths of UV-A or UV-B and cannot be captured with your gear.

 

Compare the struggle Jonathan have with the diatoms and his UV-microscope and lenses. 

[colinbm]

Thanks Ulf
Yes I am listening, but I am a deep thinker & this is driving me nuts
 

 

[enricosavazzi]

Not related to Colin's problem with epi-brightfield illumination, but probably worth noting, is that the reflecting surfaces within the tip of the barrels of BD objectives, especially in older objectives like the Zeiss ones and in reflectors that are silvered instead of aluminized, may be corroded/oxidized by exposure to a corrosive atmosphere. My Olympus BD objectives are more recent and their reflectors seem to be very resistent to degradation, but even in these objectives dust can accumulate within the reflectors.

 

Here are the reflectors from the tips of the two Olympus BD objectives I discussed above, the one on the right with some slight dust and fibers that went away afterwards with just a rubber blower. The inclination of the reflectors depends on the working distance of the objective, steeper for a higher WD. In low-WD objectives the light may need to reflect multiple times, which makes these objectives more sensitive to degradation of the epi-darkfield reflector.

 

 

PS- I prefer to call the two illumination methods epi-darkfield and epi-brightfield (shortened epi-DF and epi-BF), since strictly speaking in both types the illumination path and image path are coaxial.

[ulf]

@colinbmThe only thing for you to enhance resolution with the current setup is to go to a shorter wavelength, like 405nm.

Side illumination with the 100x objective and WD 2mm is difficult.

 

One alternative, to be approached with extreme care, always wearing orange protective goggles, is to set up the illumination with a few purple pointing lasers.

The rather monochrome light beams might give some interesting results if you are lucky, as it might give some interference with the structures.

 

As the area to be illuminated is not very big the reasonable power of a proper pointing laser might be enough.

 

[colinbm]

Thanks Ulf
I have some 385- 395 LEDs coming next week.
I have a Violet 405nm laser, I will see what I can rig-up.
I am very surprised with how little white light is needed to illuminate under the objective before things get blown out.
I really need to control the lighting down with diffusing & dimming, as well I have an adjustable aperture or iris behind the objective & that needs to be small enough not cause vignetting.
I am now using a bellows, which has made a small difference, as the M42 tubes, even with flocking were flaring too much.

 

PS, note the big wheel above the set-up, it has 400 divisions so I can now move the camera 0.0006125mm, or 0.6125um.

[ulf]

To paraphrase a known Australian actor. That's a Wheel!

https://www.youtube.com/watch?v=66niqIQ1f6c

 

[colinbm]

Yes that IS a real wheel.
I used a long cable tie & counted 400 notches. Then made the exact diameter & glued it together.
 

[ulf]

Sometimes flaring in optical structures can be fought with a few baffles, flocked and with a with well chosen sizes of their openings, to only allow the image forming beams.

 

[colinbm]

Directly above the objective you can see a ring with a + on it, that is the aperture.

 

[ulf]

Here is more on that subject:

https://www.cloudynights.com/topic/648685-refractor-baffles-for-several-upcoming-builds/

 

[colinbm]

Thanks Ulf