Barrel extention tube for Wild/Leitz objective?

albertr · Post by **albertr** » Fri May 31, 2013 6:39 pm

I have a few Wild objectives (like the one pictured below) which have short barrel and need extension tube to be used in 160mm TL microscopes. Extension tube screws in between objective and nosepiece (it can be seen on the pictures below bearing the writing "Leitz Wetzlar GERMANY Flu"). Regrettably, one of these objectives are missing that extension. Does anyone have a spare extension tube or can point me into direction where can I find one?

-albertr

rjlittlefield · Post by **rjlittlefield** » Fri May 31, 2013 6:50 pm

Does this help?

http://www.ebay.com/itm/Microscope-Obje ... 0950588769

--Rik

albertr · Post by **albertr** » Fri May 31, 2013 7:10 pm

Rik, thanks! The Leitz Flu extension tube has some glass inside... not sure if it's a lens or filter.

-albertr

rjlittlefield · Post by **rjlittlefield** » Fri May 31, 2013 8:01 pm

Interesting. I don't know anything about the Flu tube, but I'd guess that's a bit of tube length correction. Try looking at a distant scene with both eyes, then move the tube in front of one eye. If the two images no longer match, that will be a good indication that it's a lens.

--Rik

Charles Krebs · Post by **Charles Krebs** » Fri May 31, 2013 9:47 pm

That is a Leitz PLEZY adapter (Leitz made PLEZY and FLU-PLEZY adapters). The purpose was to make the older objectives (that had a shorter 37mm parfocal distance) work "nicely" together on a nosepiece with the "newer" 45mm parfocal distance. I don't know what the difference was between the two. A guess would be that the FLU-PLEZY was to be used with the Fluotar objectives.

If you have a full nosepiece of the 37mm "short barrel objectives you do not need to use the adapters on a 160mm tube length scope. But if you have a mix of 45mm parfocal and 37mm parfocal objectives on the same nosepiece then it makes life much easier to have these adapters on the older style (37mm parfocal) objectives. (Avoids crashing the objective into the slide when you rotate from a 37mm parfocal to a 45mm parfocal objective.)

If you don't have enough, a "plain" 8mm extension will do fine on most objectives. The corrective optics in the adapters are most valuable with high numerical aperture objectives. So if you have some very high NA objectives use the PLEZY on those and plain extension on the others. (If you keep an eye out on Ebay they do show up from time to time, and generally don't go for too much... maybe about $25 or so).

Pau · Post by **Pau** » Sat Jun 01, 2013 2:37 am

Charles Krebs wrote:If you don't have enough, a "plain" 8mm extension will do fine on most objectives. The corrective optics in the adapters are most valuable with high numerical aperture objectives. So if you have some very high NA objectives use the PLEZY on those and plain extension on the others...

I agree with all that Charles says but I want to point that using an empty extender, despite working fine with low NA objectives, will loss parfocality with DIN objectives and Plezy mounted ones.

Charles Krebs wrote:If you have a full nosepiece of the 37mm "short barrel objectives you do not need to use the adapters on a 160mm tube length scope.

Some DIN microscopes like my Zeiss Standard can't focus at all with short barrel objectives because the upper limit of the focusing mechanics don't raise enough the stage. In that case to use a full set of short objectives without Plezy or extenders you would need to raise the stage with longer mounting bolts and spacers (not to be recommended because doing it you will alter the adequate distance between the condenser and the slide).

Charles Krebs · Post by **Charles Krebs** » Sat Jun 01, 2013 11:22 am

Pau,

Good points. The Nikon Labophot is another example of a stand where the stage will not travel high enough to focus with short barrel objectives.

A plain extension may not be perfectly parfocal, but at least it can help avoid the most "dangerous" aspect of mixed parfocal distances on the same nosepiece... smashing a 45mm parfocal into the slide after using a short barrel. Early on, when fiddling with different objectives, I hate to think how many times I did that (:oops:) even after telling my self over and over to be careful with a "mixed" nosepiece!

albertr · Post by **albertr** » Sat Jun 01, 2013 4:36 pm

Thank to everybody who replied! I'll try to keep an eye on Ebay for PLEZY adapter...

-albertr

enricosavazzi · Post by **enricosavazzi** » Sun Jun 02, 2013 1:39 pm

albertr wrote:Rik, thanks! The Leitz Flu extension tube has some glass inside... not sure if it's a lens or filter.
-albertr

It is a filter transparent to visible light, with no detectable color cast. My guess is that it is used in visible fluorescence ("FLU") microscopy in transmitted illumination to filter out any UV that might damage the eyes or wreak havoc with photographic film.

Pau · Post by **Pau** » Sun Jun 02, 2013 2:53 pm

Charles Krebs wrote:That is a Leitz PLEZY adapter (Leitz made PLEZY and FLU-PLEZY adapters). The purpose was to make the older objectives (that had a shorter 37mm parfocal distance) work "nicely" together on a nosepiece with the "newer" 45mm parfocal distance.

enricosavazzi wrote:It is a filter transparent to visible light, with no detectable color cast.

Enrico, do you have any reference?
I've one Plezy Flu and it's definitively a very weak negative lens. I don't know if it's intended for Fluotar objectives or for Fluorescence but I'm sure it is to parfocalise short barrel with DIN objectives as Charles says. And I doubt it may have any relevant role as UV filter as fluorescence microscopes have their own filters at the filter cube (and some old ones at the eyepieces, the Leitz ones I've seen with a yellowish cast)

enricosavazzi · Post by **enricosavazzi** » Mon Jun 03, 2013 9:39 am

Pau wrote:
Charles Krebs wrote:That is a Leitz PLEZY adapter (Leitz made PLEZY and FLU-PLEZY adapters). The purpose was to make the older objectives (that had a shorter 37mm parfocal distance) work "nicely" together on a nosepiece with the "newer" 45mm parfocal distance.

enricosavazzi wrote:It is a filter transparent to visible light, with no detectable color cast.
Enrico, do you have any reference?
I've one Plezy Flu and it's definitively a very weak negative lens. I don't know if it's intended for Fluotar objectives or for Fluorescence but I'm sure it is to parfocalise short barrel with DIN objectives as Charles says. And I doubt it may have any relevant role as UV filter as fluorescence microscopes have their own filters at the filter cube (and some old ones at the eyepieces, the Leitz ones I've seen with a yellowish cast)

I have no reference, I just happen to have one of these FLU adapters. I remember looking through the filter/lens and seeing a clear image, and assumed it was just a plane window. But it does make sense to use a weak divergent lens in order to keep the optical tube length constant in spite of the added physical length. In my case I removed the optics and used the mount as an extension tube.

Doc.Al · Post by **Doc.Al** » Tue Jun 04, 2013 4:14 am

I would assume that the Flu designation is for use with fluorescence microscopy, and so would be transparent to UV light as well as visible. It is unlikely to be a barrier to UV light as suggested, as this would stop the light (in the UV range) from any fluoro epi illuminator from reaching the sample.