Some questions about microscope lenses on bellows

[seta666]

Hi,
I know very little about microscope lenses, the little knowledge I have is through this site and this usefull site
http://www.microscopyu.com/articles/optics/index.html
However I still have many doubts; the nikon E plan 10x 160/0,25 LWD is the very first of such lenses I bought; lucky me it has some CA correction, I found about eyepiece correction after buying it.
As far as I know there are achromat lenses (2-3 color correction) and apochromat lenses (full correction). Nikon CF lenses are said to be fully corrected but some are not even labelled as such.
From the other manufactures like leitz, meiji, olympus I know very little

For 4x I have the JML 21mm, which has proved an excellent performer, for 10x I need somethingt better, in some sittuations the E plan has lots of CAs and low contrast which produces more stacking artifacts/errors.
for a 10x I am considerin the Nikon BD M Plan 10x that Morpha uses, very nice contrast and CA free (at this point this is more important to me than resolution)

- What is the diference between a BD M plan and a M Plan?
any other alternatives in the 100$ range CA free?
And for 20X? is ELWD a must? any good CA free cheap candidates, 200$ or so? are olympus Dplan OK?

with one good 10x and 20x I am done, on full frame 10x sometimes is not enough ;-)

[lauriek]

There are two main differences between the Nikon BD lenses and non BD lenses (assuming all else equal, ie you're not comparing an infinity to a non infinity as well, if that makes sense).

1) The BD part means the lens has a round prism around the lens, normally in a microscope light is shone down through this collar onto the subject.

2) I think the BD lenses have a slightly different diameter screw thread mount, at least the one I have does, although that is an infinity lens so the difference may be due to that.

Actually I think (2) may well be down to the fact that my one BD lens is an infinity lens (bought before I understood the difference!) - not the fact that it's a BD lens - the thread is around 25mm, a few mm larger than the normal RMS mount Nikon M/N objectives.

I'm sure one of the more knowledgable members will be along soonish to correct anything incorrect in this post and fill you in with a bit more detail...


I've used a 20x LWD with some luck, so you don't _need_ ELWD necessarily. At 20x or above you probably wouldn't want a non LWD/ELWD lens though as the wd will likely be a mm or two which is difficult to squeeze light into!

[mgoodm3]

M plan is an RMS mount. (20 x 0.8 )

BD (non-infinity) is a M26 mount (26 x 36 tpi)

[seta666]

M plan is an RMS mount. (20 x 0.8 )

BD (non-infinity) is a M26 mount (26 x 36 tpi)

I read that BD lenses have a bigger mount as they need hollow cases, something to do with illumination. What I do not know if this has something to do with bellows
I just bought a BD 10 /0.25 210/0 for 65$, hope to try it soon
Now I am interested in a good value 20x, I am looking for good contrast, Low CAs and fair working distance (10mm or so); any suggestions?

[morfa]

I read that BD lenses have a bigger mount as they need hollow cases, something to do with illumination. What I do not know if this has something to do with bellows

It's a bit easier to find RMS->M42 (or M39 etc) adapters but since BD->RMS adapters are also available this is not very relevant.

You will need to fill the hollow barrel with something though but that's easy (just stuff something in there – or someone mentioned using a rubber o-ring of appropriate size (which seems more elegant)).

I personally prefer the BD barrels since, once the outer barrel is removed, the narrow tube containing the optics makes it easy to attach a diffuser like a ping-pong ball that can slide up and down the tube. This makes it a bit easier to access the subject without having to back away with the lens.

[seta666]

Thanks john for the "O-ring" trick, could you point out some BD-RM S adapters or alternatives(like step down rings to M42).
Do you think the BD M lenses have optical diferences with lets say M plans?
Regards

[morfa]

I use this one to mount my BD objectives in RMS mounts: http://cgi.ebay.co.uk/1-internal-and-RM ... 1479wt_913

All I've read and heard suggests that there is no optical difference between a BD M Plan and a regular M plan with the same specs. I have not had the ability to test this myself but I don't see any reason why this wouldn't be true.

[seta666]

Thanks John, I bought that adapter allready.
Regards

[ChrisLilley]

It's a bit easier to find RMS->M42 (or M39 etc) adapters but since BD->RMS adapters are also available this is not very relevant.

I recall reading (but can't find the link now) Nikon claiming that the move from RMS to 26mm was a way to make better optics with higher NA unconstrained by the narrow RMS mount.

Wouldn't a 26mm to RMS adapter defeat that advantage?

[mgoodm3]

I have a BD (same as mitutoyo) to C-mount adapter. In that transition you only go from 26 to 25 mm. The other factor is that the 26 mm BD is mostly open space on the edges anyway to allow for the funky lighting.

nikon also uses a 25 mm mount on some of their newer objectives.